Bug 1501542 - Part 1. Use -mfpu=neon to compile NEON code. r=mt

Summary:
To compile ARM's NEON code, compiler may require -mfpu=neon.

Actually, since Gecko always turn on NEON (Bug 1469790), it already uses -mfpu.
But tier-3 platform such as Linux/armeabi doesn't set -mfpu=neon as default.
So it might require this command line option.

Reviewers: mt

Bug #: 1501542

Differential Revision: https://phabricator.services.mozilla.com/D11430

--HG--
extra : rebase_source : 66cd1953edc31b5dcf04591fe2a92af3100273ac
extra : amend_source : eef93f3ca1b41109f3421907192c6811b71723f5

lib/freebl/freebl.gyp

@@ -76,11 +76,11 @@
             '__SSSE3__',
           ],
         }],
-        [ 'OS=="android"', {
-          # On Android we can't use any of the hardware acceleration :(
-          'defines!': [
-            '__ARM_NEON__',
-            '__ARM_NEON',
+        [ 'target_arch=="arm"', {
+          # Gecko doesn't support non-NEON platform on Android, but tier-3
+          # platform such as Linux/arm will need it
+          'cflags_mozilla': [
+            '-mfpu=neon'
           ],
         }],
       ],