cmake: only add large function growth param when using gcc

the param is only available in gcc so we must not add it to the CFLAGS
when compiling with clang

CMakeLists.txt

@@ -471,8 +471,10 @@ if(NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.9)
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Werror")
 endif()
 
-# Increase inlining limit to allow gcc compilation on e.g. RPi2
-set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} --param large-function-growth=1600")
+if(CMAKE_C_COMPILER_ID MATCHES "GNU")
+  # Increase inlining limit to allow gcc compilation on e.g. RPi2
+  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} --param large-function-growth=1600")
+endif(CMAKE_C_COMPILER_ID MATCHES "GNU")
 
 message(STATUS "CMAKE_C_FLAGS is ${CMAKE_C_FLAGS}")
 message(STATUS "CMAKE_CXX_FLAGS is ${CMAKE_CXX_FLAGS}")