BUG: fix for CXX only projects

Modules/Platform/Windows-cl.cmake

@@ -86,7 +86,11 @@ IF(CMAKE_GENERATOR MATCHES "Makefiles")
       "${CMAKE_ROOT}/Modules/CMakeTestNMakeCLVersion.c")
     STRING(REGEX REPLACE "/" "\\\\" testNmakeCLVersionFile "${testNmakeCLVersionFile}")
     MESSAGE(STATUS "Check for CL compiler version")
-    EXEC_PROGRAM(${CMAKE_C_COMPILER} 
+    SET(CMAKE_TEST_COMPILER ${CMAKE_C_COMPILER})
+    IF (NOT CMAKE_C_COMPILER)
+      SET(CMAKE_TEST_COMPILER ${CMAKE_CXX_COMPILER})
+    ENDIF(NOT CMAKE_C_COMPILER)
+    EXEC_PROGRAM(${CMAKE_TEST_COMPILER} 
       ARGS /nologo -EP \"${testNmakeCLVersionFile}\" 
       OUTPUT_VARIABLE CMAKE_COMPILER_OUTPUT 
       RETURN_VALUE CMAKE_COMPILER_RETURN
@@ -139,7 +143,7 @@ IF(CMAKE_GENERATOR MATCHES "Makefiles")
       "${CMAKE_ROOT}/Modules/CMakeTestForFreeVC.cxx")
     STRING(REGEX REPLACE "/" "\\\\" testForFreeVCFile "${testForFreeVCFile}")
     MESSAGE(STATUS "Check if this is a free VC compiler")
-    EXEC_PROGRAM(${CMAKE_C_COMPILER} ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp2
+    EXEC_PROGRAM(${CMAKE_TEST_COMPILER} ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp2
       ARGS /nologo /MD /EHsc
       \"${testForFreeVCFile}\"
       OUTPUT_VARIABLE CMAKE_COMPILER_OUTPUT 
@@ -160,7 +164,7 @@ IF(CMAKE_GENERATOR MATCHES "Makefiles")
     ENDIF(CMAKE_COMPILER_RETURN)
     MAKE_DIRECTORY("${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp3")
     MESSAGE(STATUS "Check CL platform")
-    EXEC_PROGRAM(${CMAKE_C_COMPILER} ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp3
+    EXEC_PROGRAM(${CMAKE_TEST_COMPILER} ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp3
       ARGS /nologo
       \"${testForFreeVCFile}\"
       /link /machine:i386