BUG: use CMAKE_COMPILER_IS_GNUCC not CMAKE_COMPILER_IS_GNUGCC

Modules/CMakeCCompiler.cmake.in

@@ -1,6 +1,6 @@
 SET(CMAKE_C_COMPILER "@CMAKE_C_COMPILER@")
 SET(CMAKE_AR "@CMAKE_AR@")
 SET(CMAKE_RANLIB "@CMAKE_RANLIB@")
-SET(CMAKE_COMPILER_IS_GNUGCC @CMAKE_COMPILER_IS_GNUGCC@)
+SET(CMAKE_COMPILER_IS_GNUCC @CMAKE_COMPILER_IS_GNUCC@)
 SET(CMAKE_C_COMPILER_LOADED 1)