Bug 1523312 - do not export msgpack, as it has no callers out side of…

… libxul r=dmajor

Includes a drive-by fix for two unused `DEFINES`.

Differential Revision: https://phabricator.services.mozilla.com/D17859

--HG--
extra : moz-landing-system : lando

third_party/msgpack/moz.build

@@ -4,7 +4,7 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-DEFINES['MSGPACK_BUILD_LIBRARY'] = True
+DEFINES['MSGPACK_DLLEXPORT'] = ''
 
 LOCAL_INCLUDES += [
     'include',

third_party/prio/moz.build

@@ -3,8 +3,6 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-DEFINES['PRIO_BUILD_LIBRARY'] = True
-
 LOCAL_INCLUDES += [
     '/security/nss/lib/freebl/mpi',
     '/third_party/msgpack/include',