Features: Include the language of the compiler in error messages.

Source/cmMakefile.cxx

@@ -4560,7 +4560,7 @@ AddRequiredTargetFeature(cmTarget *target, const std::string& feature,
       {
       e << "No";
       }
-    e << " known features for compiler\n\""
+    e << " known features for " << lang << " compiler\n\""
       << this->GetDefinition("CMAKE_" + lang + "_COMPILER_ID")
       << "\"\nversion "
       << this->GetDefinition("CMAKE_" + lang + "_COMPILER_VERSION") << ".";
@@ -4583,7 +4583,7 @@ AddRequiredTargetFeature(cmTarget *target, const std::string& feature,
     {
     cmOStringStream e;
     e << "The compiler feature \"" << feature
-      << "\" is not known to compiler\n\""
+      << "\" is not known to " << lang << " compiler\n\""
       << this->GetDefinition("CMAKE_" + lang + "_COMPILER_ID")
       << "\"\nversion "
       << this->GetDefinition("CMAKE_" + lang + "_COMPILER_VERSION") << ".";

Tests/RunCMake/CompileFeatures/NoSupportedCxxFeatures-stderr.txt

@@ -1,5 +1,5 @@
 CMake Error at NoSupportedCxxFeatures.cmake:3 \(target_compile_features\):
-  target_compile_features no known features for compiler
+  target_compile_features no known features for CXX compiler
 
   "[^"]*"
 

Tests/RunCMake/CompileFeatures/NoSupportedCxxFeaturesGenex-stderr.txt

@@ -1,5 +1,5 @@
 CMake Error in CMakeLists.txt:
-  No known features for compiler
+  No known features for CXX compiler
 
   "[^"]*"
 

Tests/RunCMake/target_compile_features/no_matching_cxx_feature-stderr.txt

@@ -1,5 +1,5 @@
 CMake Error at no_matching_cxx_feature.cmake:[0-9][0-9]? \((target_compile_features|message)\):
-  The compiler feature "[^"]+" is not known to compiler
+  The compiler feature "[^"]+" is not known to CXX compiler
 
   "[^"]*"
 

Tests/RunCMake/target_compile_features/no_matching_cxx_feature.cmake

@@ -3,7 +3,7 @@ if (NOT ";${CMAKE_CXX_COMPILE_FEATURES};" MATCHES ";gnu_cxx_typeof;"
     AND NOT ";${CMAKE_CXX_COMPILE_FEATURES};" MATCHES ";msvc_cxx_sealed;" )
   # Simulate passing the test.
   message(SEND_ERROR
-    "The compiler feature \"gnu_cxx_dummy\" is not known to compiler\n\"GNU\"\nversion 4.8.1."
+    "The compiler feature \"gnu_cxx_dummy\" is not known to CXX compiler\n\"GNU\"\nversion 4.8.1."
   )
   return()
 endif()