ERR: Disable long double warnings on xlC for the Mac.

Source/CTest/Curl/CMakeLists.txt

@@ -414,6 +414,13 @@ ELSE(RETSIGTYPE_TEST)
   SET(RETSIGTYPE int)
 ENDIF(RETSIGTYPE_TEST)
 
+IF(CMAKE_COMPILER_IS_GNUCC AND APPLE)
+  # The Mac version of GCC warns about use of long double.  Disable it.
+  GET_SOURCE_FILE_PROPERTY(MPRINTF_COMPILE_FLAGS mprintf.c COMPILE_FLAGS)
+  SET_SOURCE_FILES_PROPERTIES(mprintf.c PROPERTIES
+    COMPILE_FLAGS "${MPRINTF_COMPILE_FLAGS} -Wno-long-double")
+ENDIF(CMAKE_COMPILER_IS_GNUCC AND APPLE)
+
 # The rest of the build
 
 INCLUDE_DIRECTORIES(${LIBCURL_SOURCE_DIR})