Change the test file for stackprotector for clang

Now compiles with clang !

cmake/Modules/DefineCompilerFlags.cmake

@@ -1,6 +1,7 @@
 # define system dependent compiler flags
 
 include(CheckCCompilerFlag)
+include(MacroCheckCCompilerFlagSSP)
 
 if (UNIX AND NOT WIN32)
   if (${CMAKE_C_COMPILER_ID} MATCHES GNU)
@@ -13,7 +14,7 @@ if (UNIX AND NOT WIN32)
       set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fPIC")
     endif (WITH_FPIC)
 
-    check_c_compiler_flag("-fstack-protector" WITH_STACK_PROTECTOR)
+    check_c_compiler_flag_ssp("-fstack-protector" WITH_STACK_PROTECTOR)
     if (WITH_STACK_PROTECTOR)
       set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fstack-protector")
     endif (WITH_STACK_PROTECTOR)

cmake/Modules/MacroCheckCCompilerFlagSSP.cmake

@@ -0,0 +1,25 @@
+# - Check whether the C compiler supports a given flag.
+# CHECK_C_COMPILER_FLAG(FLAG VARIABLE)
+#
+#  FLAG - the compiler flag
+#  VARIABLE - variable to store the result
+# 
+#  This actually calls the check_c_source_compiles macro.
+#  See help for CheckCSourceCompiles for a listing of variables
+#  that can modify the build.
+
+# Copyright (c) 2006, Alexander Neundorf, <neundorf@kde.org>
+#
+# Redistribution and use is allowed according to the terms of the BSD license.
+# For details see the accompanying COPYING-CMAKE-SCRIPTS file.
+
+
+INCLUDE(CheckCSourceCompiles)
+
+MACRO (CHECK_C_COMPILER_FLAG_SSP _FLAG _RESULT)
+   SET(SAFE_CMAKE_REQUIRED_DEFINITIONS "${CMAKE_REQUIRED_DEFINITIONS}")
+   SET(CMAKE_REQUIRED_DEFINITIONS "${_FLAG}")
+   CHECK_C_SOURCE_COMPILES("int main(int argc, char **argv) { char buffer[256]; return buffer[argc]=0;}" ${_RESULT})
+   SET (CMAKE_REQUIRED_DEFINITIONS "${SAFE_CMAKE_REQUIRED_DEFINITIONS}")
+ENDMACRO (CHECK_C_COMPILER_FLAG_SSP)
+