cmGlobalGenerator: hint about missing extensions on Windows

Discussed on Discourse:

    https://discourse.cmake.org/t/cross-compiling-from-a-windows-host-targeting-raspbian-32-bits-arm/9250

Source/cmGlobalGenerator.cxx

@@ -874,7 +874,11 @@ void cmGlobalGenerator::EnableLanguage(
         noCompiler <<
           "The " << compilerName << ":\n"
           "  " << *compilerFile << "\n"
-          "is not a full path and was not found in the PATH.\n"
+          "is not a full path and was not found in the PATH."
+#ifdef _WIN32
+          "  Perhaps the extension is missing?"
+#endif
+          "\n"
           ;
         /* clang-format on */
       } else if (!cmSystemTools::FileExists(*compilerFile)) {

Tests/RunCMake/CompilerNotFound/BadCompilerC-stderr-JOM.txt

@@ -3,7 +3,8 @@ CMake Error at BadCompilerC.cmake:2 \(enable_language\):
 
     no-C-compiler
 
-  is not a full path and was not found in the PATH.
+  is not a full path and was not found in the PATH.(  Perhaps the extension is
+  missing\?)?
 
   To use the JOM generator with Visual C\+\+, cmake must be run from a shell
   that can use the compiler cl from the command line.  This environment is

Tests/RunCMake/CompilerNotFound/BadCompilerC-stderr-NMake.txt

@@ -3,7 +3,8 @@ CMake Error at BadCompilerC.cmake:2 \(enable_language\):
 
     no-C-compiler
 
-  is not a full path and was not found in the PATH.
+  is not a full path and was not found in the PATH.(  Perhaps the extension is
+  missing\?)?
 
   To use the NMake generator with Visual C\+\+, cmake must be run from a shell
   that can use the compiler cl from the command line.  This environment is

Tests/RunCMake/CompilerNotFound/BadCompilerC-stderr.txt

@@ -3,7 +3,8 @@ CMake Error at BadCompilerC.cmake:2 \(enable_language\):
 
     no-C-compiler
 
-  is not a full path and was not found in the PATH.
+  is not a full path and was not found in the PATH.(  Perhaps the extension is
+  missing\?)?
 
   Tell CMake where to find the compiler by setting either the environment
   variable "CC" or the CMake cache entry CMAKE_C_COMPILER to the full path to

Tests/RunCMake/CompilerNotFound/BadCompilerCXX-stderr-JOM.txt

@@ -3,7 +3,8 @@ CMake Error at BadCompilerCXX.cmake:2 \(enable_language\):
 
     no-CXX-compiler
 
-  is not a full path and was not found in the PATH.
+  is not a full path and was not found in the PATH.(  Perhaps the extension is
+  missing\?)?
 
   To use the JOM generator with Visual C\+\+, cmake must be run from a shell
   that can use the compiler cl from the command line.  This environment is

Tests/RunCMake/CompilerNotFound/BadCompilerCXX-stderr-NMake.txt

@@ -3,7 +3,8 @@ CMake Error at BadCompilerCXX.cmake:2 \(enable_language\):
 
     no-CXX-compiler
 
-  is not a full path and was not found in the PATH.
+  is not a full path and was not found in the PATH.(  Perhaps the extension is
+  missing\?)?
 
   To use the NMake generator with Visual C\+\+, cmake must be run from a shell
   that can use the compiler cl from the command line.  This environment is

Tests/RunCMake/CompilerNotFound/BadCompilerCXX-stderr.txt

@@ -3,7 +3,8 @@ CMake Error at BadCompilerCXX.cmake:2 \(enable_language\):
 
     no-CXX-compiler
 
-  is not a full path and was not found in the PATH.
+  is not a full path and was not found in the PATH.(  Perhaps the extension is
+  missing\?)?
 
   Tell CMake where to find the compiler by setting either the environment
   variable "CXX" or the CMake cache entry CMAKE_CXX_COMPILER to the full path

Tests/RunCMake/CompilerNotFound/BadCompilerCandCXX-stderr-JOM.txt

@@ -3,7 +3,8 @@ CMake Error at BadCompilerCandCXX.cmake:3 \(project\):
 
     no-C-compiler
 
-  is not a full path and was not found in the PATH.
+  is not a full path and was not found in the PATH.(  Perhaps the extension is
+  missing\?)?
 
   To use the JOM generator with Visual C\+\+, cmake must be run from a shell
   that can use the compiler cl from the command line.  This environment is
@@ -21,7 +22,8 @@ CMake Error at BadCompilerCandCXX.cmake:3 \(project\):
 
     no-CXX-compiler
 
-  is not a full path and was not found in the PATH.
+  is not a full path and was not found in the PATH.(  Perhaps the extension is
+  missing\?)?
 
   To use the JOM generator with Visual C\+\+, cmake must be run from a shell
   that can use the compiler cl from the command line.  This environment is

Tests/RunCMake/CompilerNotFound/BadCompilerCandCXX-stderr-NMake.txt

@@ -3,7 +3,8 @@ CMake Error at BadCompilerCandCXX.cmake:3 \(project\):
 
     no-C-compiler
 
-  is not a full path and was not found in the PATH.
+  is not a full path and was not found in the PATH.(  Perhaps the extension is
+  missing\?)?
 
   To use the NMake generator with Visual C\+\+, cmake must be run from a shell
   that can use the compiler cl from the command line.  This environment is
@@ -21,7 +22,8 @@ CMake Error at BadCompilerCandCXX.cmake:3 \(project\):
 
     no-CXX-compiler
 
-  is not a full path and was not found in the PATH.
+  is not a full path and was not found in the PATH.(  Perhaps the extension is
+  missing\?)?
 
   To use the NMake generator with Visual C\+\+, cmake must be run from a shell
   that can use the compiler cl from the command line.  This environment is

Tests/RunCMake/CompilerNotFound/BadCompilerCandCXX-stderr.txt

@@ -3,7 +3,8 @@ CMake Error at BadCompilerCandCXX.cmake:3 \(project\):
 
     no-C-compiler
 
-  is not a full path and was not found in the PATH.
+  is not a full path and was not found in the PATH.(  Perhaps the extension is
+  missing\?)?
 
   Tell CMake where to find the compiler by setting either the environment
   variable "CC" or the CMake cache entry CMAKE_C_COMPILER to the full path to
@@ -16,7 +17,8 @@ CMake Error at BadCompilerCandCXX.cmake:3 \(project\):
 
     no-CXX-compiler
 
-  is not a full path and was not found in the PATH.
+  is not a full path and was not found in the PATH.(  Perhaps the extension is
+  missing\?)?
 
   Tell CMake where to find the compiler by setting either the environment
   variable "CXX" or the CMake cache entry CMAKE_CXX_COMPILER to the full path