Do not warn about using the clang compiler when building botan

Change-Id: Iec594b1a7afb5d80148c496f1842ea41dab8ef7b
Reviewed-by: Christian Kandeler <christian.kandeler@nokia.com>

src/libs/3rdparty/botan/botan.pro

@@ -20,6 +20,7 @@ unix:DEFINES += BOTAN_TARGET_OS_HAS_GETTIMEOFDAY BOTAN_HAS_ALLOC_MMAP \
     BOTAN_HAS_DYNAMICALLY_LOADED_ENGINE BOTAN_HAS_DYNAMIC_LOADER
 macx:DEFINES += BOTAN_TARGET_OS_IS_DARWIN
 *g++*:DEFINES += BOTAN_BUILD_COMPILER_IS_GCC
+*clang*:DEFINES += BOTAN_BUILD_COMPILER_IS_CLANG
 
 win32 {
     DEFINES += BOTAN_TARGET_OS_IS_WINDOWS \