[evolution-data-server] SetupBuildFlags.cmake: Check C++ flags only if C++ is enabled

[Milan Crha <mcrha src gnome org>]

commit 9c501418114b6d48df9c4be228111a52cdb860d2
Author: Milan Crha <mcrha redhat com>
Date:   Thu Nov 10 15:48:16 2016 +0100

    SetupBuildFlags.cmake: Check C++ flags only if C++ is enabled

 cmake/modules/SetupBuildFlags.cmake |   21 +++++++++++++--------
 1 files changed, 13 insertions(+), 8 deletions(-)
---
diff --git a/cmake/modules/SetupBuildFlags.cmake b/cmake/modules/SetupBuildFlags.cmake
index a7d2aa4..3221591 100644
--- a/cmake/modules/SetupBuildFlags.cmake
+++ b/cmake/modules/SetupBuildFlags.cmake
@@ -3,7 +3,10 @@
 # Setups compiler/linker flags, skipping those which are not supported.
 
 include(CheckCCompilerFlag)
-include(CheckCXXCompilerFlag)
+
+if(CMAKE_CXX_COMPILER_ID)
+       include(CheckCXXCompilerFlag)
+endif(CMAKE_CXX_COMPILER_ID)
 
 macro(setup_build_flags _maintainer_mode)
        list(APPEND proposed_flags
@@ -64,13 +67,15 @@ macro(setup_build_flags _maintainer_mode)
                unset(c_flag_${flag}_supported)
        endforeach()
 
-       foreach(flag IN LISTS proposed_cxx_flags)
-               check_cxx_compiler_flag(${flag} cxx_flag_${flag}_supported)
-               if(cxx_flag_${flag}_supported)
-                       set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${flag}")
-               endif(cxx_flag_${flag}_supported)
-               unset(cxx_flag_${flag}_supported)
-       endforeach()
+       if(CMAKE_CXX_COMPILER_ID)
+               foreach(flag IN LISTS proposed_cxx_flags)
+                       check_cxx_compiler_flag(${flag} cxx_flag_${flag}_supported)
+                       if(cxx_flag_${flag}_supported)
+                               set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${flag}")
+                       endif(cxx_flag_${flag}_supported)
+                       unset(cxx_flag_${flag}_supported)
+               endforeach()
+       endif(CMAKE_CXX_COMPILER_ID)
 
        if(("${CMAKE_C_COMPILER_ID}" STREQUAL "Clang") OR ("${CMAKE_C_COMPILER_ID}" STREQUAL "GNU"))
                set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -Wl,--no-undefined")