cmake: Fix not detecting unsupported g++ related warning checks

Unsupported warnings are detected by cmake through errors during
compilation, which causes g++ not to detect them, since they are
only output as warnings. Setting -Werror ensures this.

Signed-off-by: Ralf Habacker <ralf.habacker@freenet.de>

diff --git a/cmake/modules/Macros.cmake b/cmake/modules/Macros.cmake
index 8d021d37245bacbfc22a13e77615787ad079838c..04ee287d3671afac3ec7ec0803539f4b444c8a9f 100644 (file)
--- a/cmake/modules/Macros.cmake
+++ b/cmake/modules/Macros.cmake
@@ -124,6 +124,8 @@ include(CheckCCompilerFlag)
 include(CheckCXXCompilerFlag)
 function(check_compiler_warning_flag _flag _result _cxx)
     string(MAKE_C_IDENTIFIER "${_flag}" _varname)
+    # required to get errors
+    list(APPEND _flag -Werror)
     if (_cxx)
         check_cxx_compiler_flag("${_flag}" HAVE_CXX_FLAG${_varname})
         set(${_result} ${HAVE_CXX_FLAG${_varname}} PARENT_SCOPE)