Bug 1516605 - Turn on NEON on aarch64 when using gcc or clang. r=aosmond

libpng has NEON support using intrinsics, not assembler, so we should use it
even if aarch64.

MSVC build still turns off NEON since libpng doesn't support it on stable
version although upstream has it.

Differential Revision: https://phabricator.services.mozilla.com/D15462

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

media/libpng/moz.build

@@ -41,6 +41,13 @@ if CONFIG['CPU_ARCH'] == 'arm':
         'arm/filter_neon.S'
     ]
 
+if CONFIG['CPU_ARCH'] == 'aarch64' and CONFIG['CC_TYPE'] in ('clang', 'gcc'):
+    DEFINES['MOZ_PNG_USE_ARM_NEON'] = True
+    UNIFIED_SOURCES += [
+        'arm/arm_init.c',
+        'arm/filter_neon_intrinsics.c'
+    ]
+
 if CONFIG['INTEL_ARCHITECTURE']:
     DEFINES['MOZ_PNG_USE_INTEL_SSE'] = True
     UNIFIED_SOURCES += [