ENH: use c not cxx

Modules/Platform/IRIX64.cmake

@@ -5,7 +5,7 @@ SET(CMAKE_SHARED_LIBRARY_RUNTIME_C_FLAG "-Wl,-rpath,")       # -rpath
 SET(CMAKE_SHARED_LIBRARY_RUNTIME_C_FLAG_SEP "")   # : or empty
 SET(CMAKE_SHARED_LIBRARY_SONAME_C_FLAG "-Wl,-soname,")
 SET(CMAKE_SHARED_LIBRARY_SONAME_CXX_FLAG "-Wl,-soname,")
-IF(NOT CMAKE_COMPILER_IS_GNUCXX)
+IF(NOT CMAKE_COMPILER_IS_GNUCC)
   # Set default flags init.
   SET(CMAKE_C_FLAGS_INIT "")
   SET(CMAKE_CXX_FLAGS_INIT "")
@@ -42,4 +42,4 @@ IF(NOT CMAKE_COMPILER_IS_GNUCXX)
   SET (CMAKE_CXX_FLAGS_MINSIZEREL_INIT "-O3 -DNDEBUG")
   SET (CMAKE_CXX_FLAGS_RELEASE_INIT "-O2 -DNDEBUG")
   SET (CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT "-O2")
-ENDIF(NOT CMAKE_COMPILER_IS_GNUCXX)
+ENDIF(NOT CMAKE_COMPILER_IS_GNUCC)