Bug 1756260 - part10 : fix macOS build error. r=media-playback-reviewers,bryce

> /builds/worker/fetches/MacOSX10.12.sdk/usr/include/MacTypes.h:542:16: error: reference to 'Point' is ambiguous

The point type conflicts with the `gfx::Point`, so move the media data out of the unify build.

Differential Revision: https://phabricator.services.mozilla.com/D146021

dom/media/moz.build

@@ -280,7 +280,6 @@ UNIFIED_SOURCES += [
     "ImageToI420.cpp",
     "MediaCache.cpp",
     "MediaContainerType.cpp",
-    "MediaData.cpp",
     "MediaDecoder.cpp",
     "MediaDecoderStateMachine.cpp",
     "MediaDecoderStateMachineBase.cpp",
@@ -325,9 +324,11 @@ else:
 # CubebUtils.cpp needs to be built separately due to what appears to be some kind
 # of compiler bug on Android 4.2 x86 opt. See bug 1408459.
 # DecoderTraits.cpp needs to be built separately because of Mac OS X headers.
+# MediaData.cpp : ambiguous compilation error caused by Mac OS X headers.
 SOURCES += [
     "CubebUtils.cpp",
     "DecoderTraits.cpp",
+    "MediaData.cpp",
 ]
 
 # Some codec-related code uses multi-character constants, which GCC and clang