The SetEnv.cmd script that the "SDK command prompt" shortcut installed with Windows SDK 7.1 erroneously runs checks for cl.exe in various places before adding any entries to PATH. So it fails to add anything if a native C compiler is not installed, even if .NET tools are.
A workaround is to run the Windows SDK 7.1 installer and install the SDK's native C++ toolchain, too.
A real fix is to apply the below patch to SetEnv.cmd
It resides under <SDK install dir>\Bin\SetEnv.cmd. This will also fix missing paths to other tools located in <SDK install dir>\Bin and subfolders.
--- SetEnv.Cmd_ 2010-04-27 19:52:00.000000000 +0400
+++ SetEnv.Cmd  2013-12-02 15:05:30.834400000 +0400
@@ -228,10 +228,10 @@
 
 IF "%CURRENT_CPU%" =="x64" (
   IF "%TARGET_CPU%" == "x64" (
+    SET "FxTools=%FrameworkDir64%\%FrameworkVersion%;%FrameworkDir32%%FrameworkVersion%;%windir%\Microsoft.NET\Framework64\v3.5;%windir%\Microsoft.NET\Framework\v3.5;"
+    SET "SdkTools=%WindowsSdkDir%Bin\NETFX 4.0 Tools\x64;%WindowsSdkDir%Bin\x64;%WindowsSdkDir%Bin;"
     IF EXIST "%VCTools%\amd64\cl.exe" (
       SET "VCTools=%VCTools%\amd64;%VCTools%\VCPackages;"
-      SET "SdkTools=%WindowsSdkDir%Bin\NETFX 4.0 Tools\x64;%WindowsSdkDir%Bin\x64;%WindowsSdkDir%Bin;"
-      SET "FxTools=%FrameworkDir64%\%FrameworkVersion%;%FrameworkDir32%%FrameworkVersion%;%windir%\Microsoft.NET\Framework64\v3.5;%windir%\Microsoft.NET\Framework\v3.5;"
     ) ELSE (
       SET VCTools=
       ECHO The x64 compilers are not currently installed.
@@ -239,10 +239,10 @@
       ECHO .
     )
   ) ELSE IF "%TARGET_CPU%" == "IA64" (
+    SET "FxTools=%FrameworkDir64%\%FrameworkVersion%;%FrameworkDir32%%FrameworkVersion%;%windir%\Microsoft.NET\Framework64\v3.5;%windir%\Microsoft.NET\Framework\v3.5;"
+    SET "SdkTools=%WindowsSdkDir%Bin\NETFX 4.0 Tools\x64;%WindowsSdkDir%Bin\x64;%WindowsSdkDir%Bin;"
     IF EXIST "%VCTools%\x86_ia64\cl.exe" (
       SET "VCTools=%VCTools%\x86_ia64;%VCTools%\VCPackages;"
-      SET "SdkTools=%WindowsSdkDir%Bin\NETFX 4.0 Tools\x64;%WindowsSdkDir%Bin\x64;%WindowsSdkDir%Bin;"
-      SET "FxTools=%FrameworkDir64%\%FrameworkVersion%;%FrameworkDir32%%FrameworkVersion%;%windir%\Microsoft.NET\Framework64\v3.5;%windir%\Microsoft.NET\Framework\v3.5;"
     ) ELSE (
       SET VCTools=
       ECHO The IA64 compilers are not currently installed.
@@ -250,10 +250,10 @@
       ECHO .
     )
   ) ELSE IF "%TARGET_CPU%" == "x86" (
+    SET "FxTools=%FrameworkDir32%%FrameworkVersion%;%windir%\Microsoft.NET\Framework\v3.5;"
+    SET "SdkTools=%WindowsSdkDir%Bin\NETFX 4.0 Tools;%WindowsSdkDir%Bin;"
     IF EXIST "%VCTools%\cl.exe" (
       SET "VCTools=%VCTools%;%VCTools%\VCPackages;"
-      SET "SdkTools=%WindowsSdkDir%Bin\NETFX 4.0 Tools;%WindowsSdkDir%Bin;"
-      SET "FxTools=%FrameworkDir32%%FrameworkVersion%;%windir%\Microsoft.NET\Framework\v3.5;"
     ) ELSE (
       SET VCTools=
       ECHO The x86 compilers are not currently installed.
@@ -263,10 +263,10 @@
   )
 ) ELSE IF "%CURRENT_CPU%" =="IA64" (
   IF "%TARGET_CPU%" == "IA64" (
+    SET "FxTools=%FrameworkDir64%\%FrameworkVersion%;%FrameworkDir32%%FrameworkVersion%;%windir%\Microsoft.NET\Framework64\v3.5;%windir%\Microsoft.NET\Framework\v3.5;"
+    SET "SdkTools=%WindowsSdkDir%Bin\NETFX 4.0 Tools\IA64;%WindowsSdkDir%Bin\IA64;%WindowsSdkDir%Bin;"
     IF EXIST "%VCTools%\IA64\cl.exe" (
       SET "VCTools=%VCTools%\IA64;%VCTools%;%VCTools%\VCPackages;"
-      SET "SdkTools=%WindowsSdkDir%Bin\NETFX 4.0 Tools\IA64;%WindowsSdkDir%Bin\IA64;%WindowsSdkDir%Bin;"
-      SET "FxTools=%FrameworkDir64%\%FrameworkVersion%;%FrameworkDir32%%FrameworkVersion%;%windir%\Microsoft.NET\Framework64\v3.5;%windir%\Microsoft.NET\Framework\v3.5;"
     ) ELSE (
       SET VCTools=
       ECHO The IA64 compilers are not currently installed.
@@ -274,10 +274,10 @@
       ECHO .
     )
   ) ELSE IF "%TARGET_CPU%" == "x64" (
+    SET "FxTools=%FrameworkDir64%\%FrameworkVersion%;%FrameworkDir32%%FrameworkVersion%;%windir%\Microsoft.NET\Framework64\v3.5;%windir%\Microsoft.NET\Framework\v3.5;"
+    SET "SdkTools=%WindowsSdkDir%Bin\NETFX 4.0 Tools\IA64;%WindowsSdkDir%Bin\IA64;%WindowsSdkDir%Bin;"
     IF EXIST "%VCTools%\x86_amd64\cl.exe" (
       SET "VCTools=%VCTools%\x86_amd64;%VCTools%\VCPackages;"
-      SET "SdkTools=%WindowsSdkDir%Bin\NETFX 4.0 Tools\IA64;%WindowsSdkDir%Bin\IA64;%WindowsSdkDir%Bin;"
-      SET "FxTools=%FrameworkDir64%\%FrameworkVersion%;%FrameworkDir32%%FrameworkVersion%;%windir%\Microsoft.NET\Framework64\v3.5;%windir%\Microsoft.NET\Framework\v3.5;"
     ) ELSE (
       SET VCTools=
       ECHO The VC compilers are not currently installed.
@@ -285,10 +285,10 @@
       ECHO .
     )
   ) ELSE IF "%TARGET_CPU%" == "x86" (
+    SET "FxTools=%FrameworkDir32%%FrameworkVersion%;%windir%\Microsoft.NET\Framework\v3.5;"
+    SET "SdkTools=%WindowsSdkDir%Bin\NETFX 4.0 Tools;%WindowsSdkDir%Bin;"
     IF EXIST "%VCTools%\cl.exe" (
       SET "VCTools=%VCTools%;%VCTools%\VCPackages;"
-      SET "SdkTools=%WindowsSdkDir%Bin\NETFX 4.0 Tools;%WindowsSdkDir%Bin;"
-      SET "FxTools=%FrameworkDir32%%FrameworkVersion%;%windir%\Microsoft.NET\Framework\v3.5;"
     ) ELSE (
       SET VCTools=
       ECHO The x86 compilers are not currently installed.
@@ -298,10 +298,10 @@
   )
 ) ELSE IF "%CURRENT_CPU%"=="x86" (
   IF "%TARGET_CPU%" == "x64" (
+    SET "FxTools=%FrameworkDir32%%FrameworkVersion%;%windir%\Microsoft.NET\Framework\v3.5;"
+    SET "SdkTools=%WindowsSdkDir%Bin\NETFX 4.0 Tools;%WindowsSdkDir%Bin;"
     IF EXIST "%VCTools%\x86_amd64\cl.exe" (
       SET "VCTools=%VCTools%\x86_amd64;%VCTools%\VCPackages;"
-      SET "SdkTools=%WindowsSdkDir%Bin\NETFX 4.0 Tools;%WindowsSdkDir%Bin;"
-      SET "FxTools=%FrameworkDir32%%FrameworkVersion%;%windir%\Microsoft.NET\Framework\v3.5;"
     ) ELSE (
       SET VCTools=
       ECHO The x64 cross compilers are not currently installed.
@@ -309,10 +309,10 @@
       ECHO .
     )
   ) ELSE IF "%TARGET_CPU%" == "IA64" (
+    SET "FxTools=%FrameworkDir32%%FrameworkVersion%;%windir%\Microsoft.NET\Framework\v3.5;"
+    SET "SdkTools=%WindowsSdkDir%Bin\NETFX 4.0 Tools;%WindowsSdkDir%Bin;"
     IF EXIST "%VCTools%\x86_IA64\cl.exe" (
       SET "VCTools=%VCTools%\x86_IA64;%VCTools%;%VCTools%\VCPackages;"
-      SET "SdkTools=%WindowsSdkDir%Bin\NETFX 4.0 Tools;%WindowsSdkDir%Bin;"
-      SET "FxTools=%FrameworkDir32%%FrameworkVersion%;%windir%\Microsoft.NET\Framework\v3.5;"
     ) ELSE (
       SET VCTools=
       ECHO The IA64 compilers are not currently installed.
@@ -320,10 +320,10 @@
       ECHO .
     )
   ) ELSE IF "%TARGET_CPU%" == "x86" (
+    SET "FxTools=%FrameworkDir32%%FrameworkVersion%;%windir%\Microsoft.NET\Framework\v3.5;"
+    SET "SdkTools=%WindowsSdkDir%Bin\NETFX 4.0 Tools;%WindowsSdkDir%Bin;"
     IF EXIST "%VCTools%\cl.exe" (
       SET "VCTools=%VCTools%;%VCTools%\VCPackages;"
-      SET "SdkTools=%WindowsSdkDir%Bin\NETFX 4.0 Tools;%WindowsSdkDir%Bin;"
-      SET "FxTools=%FrameworkDir32%%FrameworkVersion%;%windir%\Microsoft.NET\Framework\v3.5;"
     ) ELSE (
       SET VCTools=
       ECHO The x86 compilers are not currently installed. x86-x86
@@ -331,15 +331,17 @@
       ECHO .
     )
   )
-) ELSE IF EXIST "%VCTools%\cl.exe" (
-  SET "VCTools=%VCTools%;%VCTools%\VCPackages;"
-  SET "SdkTools=%WindowsSdkDir%Bin\NETFX 4.0 Tools;%WindowsSdkDir%Bin;"
-  SET "FxTools=%FrameworkDir32%%FrameworkVersion%;%windir%\Microsoft.NET\Framework\v3.5;"
 ) ELSE (
-  SET VCTools=
-  ECHO The x86 compilers are not currently installed. default
-  ECHO Please go to Add/Remove Programs to update your installation.
-  ECHO .
+  SET "FxTools=%FrameworkDir32%%FrameworkVersion%;%windir%\Microsoft.NET\Framework\v3.5;"
+  SET "SdkTools=%WindowsSdkDir%Bin\NETFX 4.0 Tools;%WindowsSdkDir%Bin;"
+  IF EXIST "%VCTools%\cl.exe" (
+    SET "VCTools=%VCTools%;%VCTools%\VCPackages;"
+  ) ELSE (
+    SET VCTools=
+    ECHO The x86 compilers are not currently installed. default
+    ECHO Please go to Add/Remove Programs to update your installation.
+    ECHO .
+  )
 )
 
 :: --------------------------------------------------------------------------------------------