Tests: Make CompileFeatures feature list lang-specific.

Tests/RunCMake/CompileFeatures/RunCMakeTest.cmake

@@ -10,11 +10,11 @@ run_cmake(NotAFeature_OriginDebug_target_compile_features)
 
 run_cmake(generate_feature_list)
 file(READ
-  "${RunCMake_BINARY_DIR}/generate_feature_list-build/features.txt"
-  FEATURES
+  "${RunCMake_BINARY_DIR}/generate_feature_list-build/cxx_features.txt"
+  CXX_FEATURES
 )
 
-if (NOT FEATURES)
+if (NOT CXX_FEATURES)
   run_cmake(NoSupportedCxxFeatures)
   run_cmake(NoSupportedCxxFeaturesGenex)
 endif()

Tests/RunCMake/CompileFeatures/generate_feature_list.cmake

@@ -1,5 +1,5 @@
 
-file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/features.txt"
+file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/cxx_features.txt"
   "${CMAKE_CXX_COMPILE_FEATURES}"
 )