jjb: babeltrace: ignore pragma warnings on MacOS

jjb: babeltrace: ignore pragma warnings on MacOS

Ignore prama warnings from Glib on MacOS

  plugin.c:85:4: warning: Deprecated pre-processor symbol [-W#pragma-messages]
                          PYTHON_PLUGIN_PROVIDER_FILENAME, NULL);
                          ^
  plugin.c:36:79: note: expanded from macro 'PYTHON_PLUGIN_PROVIDER_FILENAME'
  #define PYTHON_PLUGIN_PROVIDER_FILENAME "babeltrace2-python-plugin-provider." G_MODULE_SUFFIX
                                                                                ^
  /opt/local/lib/glib-2.0/include/glibconfig.h:289:30: note: expanded from macro 'G_MODULE_SUFFIX'
  #define G_MODULE_SUFFIX "so" GLIB_DEPRECATED_MACRO_IN_2_76
                               ^
  /opt/local/include/glib-2.0/glib/glib-visibility.h:889:39: note: expanded from macro 'GLIB_DEPRECATED_MACRO_IN_2_76'
  #define GLIB_DEPRECATED_MACRO_IN_2_76 GLIB_DEPRECATED_MACRO
                                        ^
  /opt/local/include/glib-2.0/glib/gmacros.h:1297:31: note: expanded from macro 'GLIB_DEPRECATED_MACRO'
  #define GLIB_DEPRECATED_MACRO _GLIB_GNUC_DO_PRAGMA(GCC warning "Deprecated pre-processor symbol")
                                ^
  /opt/local/include/glib-2.0/glib/gmacros.h:1296:33: note: expanded from macro '_GLIB_GNUC_DO_PRAGMA'
  #define _GLIB_GNUC_DO_PRAGMA(x) _Pragma(G_STRINGIFY (x))
                                  ^
  <scratch space>:11:6: note: expanded from here
   GCC warning "Deprecated pre-processor symbol"
       ^

Change-Id: Iacccd4949caf618e67b94987ab2e9511b33958d1
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>