Add compile flags and test for compiler options only if we use gcc.

cmake/Modules/DefineCompilerFlags.cmake

@@ -3,49 +3,48 @@
 include(CheckCCompilerFlag)
 
 if (UNIX AND NOT WIN32)
-  # with -fPIC
-  check_c_compiler_flag("-fPIC" WITH_FPIC)
-  if (WITH_FPIC)
-    add_definitions(-fPIC)
-  endif (WITH_FPIC)
-
-  if (CMAKE_SIZEOF_VOID_P MATCHES "8")
-    # with large file support
-    execute_process(
-      COMMAND
-        getconf LFS64_CFLAGS
-      OUTPUT_VARIABLE
-        _lfs_CFLAGS
-      ERROR_QUIET
-      OUTPUT_STRIP_TRAILING_WHITESPACE
-  )
-  else (CMAKE_SIZEOF_VOID_P MATCHES "8")
-    # with large file support
-    execute_process(
-      COMMAND
-        getconf LFS_CFLAGS
-      OUTPUT_VARIABLE
-        _lfs_CFLAGS
-      ERROR_QUIET
-      OUTPUT_STRIP_TRAILING_WHITESPACE
-    )
-    string(REGEX REPLACE "[\r\n]" " " "${_lfs_CFLAGS}" "${${_lfs_CFLAGS}}")
-
-    add_definitions(${_lfs_CFLAGS})
-  endif (CMAKE_SIZEOF_VOID_P MATCHES "8")
-
   if (CMAKE_COMPILER_IS_GNUCC)
     add_definitions(-Wall -Wextra -Wmissing-prototypes -Wdeclaration-after-statement -Wunused)
+
+    # with -fPIC
+    check_c_compiler_flag("-fPIC" WITH_FPIC)
+    if (WITH_FPIC)
+      add_definitions(-fPIC)
+    endif (WITH_FPIC)
+
+    if (CMAKE_SIZEOF_VOID_P MATCHES "8")
+      # with large file support
+      execute_process(
+        COMMAND
+          getconf LFS64_CFLAGS
+        OUTPUT_VARIABLE
+          _lfs_CFLAGS
+        ERROR_QUIET
+        OUTPUT_STRIP_TRAILING_WHITESPACE
+    )
+    else (CMAKE_SIZEOF_VOID_P MATCHES "8")
+      # with large file support
+      execute_process(
+        COMMAND
+          getconf LFS_CFLAGS
+        OUTPUT_VARIABLE
+          _lfs_CFLAGS
+        ERROR_QUIET
+        OUTPUT_STRIP_TRAILING_WHITESPACE
+      )
+      string(REGEX REPLACE "[\r\n]" " " "${_lfs_CFLAGS}" "${${_lfs_CFLAGS}}")
+
+      add_definitions(${_lfs_CFLAGS})
+    endif (CMAKE_SIZEOF_VOID_P MATCHES "8")
+
+    check_c_compiler_flag("-fstack-protector" WITH_STACK_PROTECTOR)
+    if (WITH_STACK_PROTECTOR)
+      add_definitions(-fstack-protector)
+    endif (WITH_STACK_PROTECTOR)
+
+    check_c_compiler_flag("-D_FORTIFY_SOURCE=2" WITH_FORTIFY_SOURCE)
+    if (WITH_FORTIFY_SOURCE)
+      add_definitions(-D_FORTIFY_SOURCE=2)
+    endif (WITH_FORTIFY_SOURCE)
   endif (CMAKE_COMPILER_IS_GNUCC)
-
-  check_c_compiler_flag("-fstack-protector" WITH_STACK_PROTECTOR)
-  if (WITH_STACK_PROTECTOR)
-    add_definitions(-fstack-protector)
-  endif (WITH_STACK_PROTECTOR)
-
-  check_c_compiler_flag("-D_FORTIFY_SOURCE=2" WITH_FORTIFY_SOURCE)
-  if (WITH_FORTIFY_SOURCE)
-    add_definitions(-D_FORTIFY_SOURCE=2)
-  endif (WITH_FORTIFY_SOURCE)
-
 endif (UNIX AND NOT WIN32)