Bug 1560183 - Re-enable the RDD Process for MinGW builds r=jya

Bug 1557844 fixed (inadvertently) the failures we were getting with RDD

Differential Revision: https://phabricator.services.mozilla.com/D38263

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

modules/libpref/init/StaticPrefList.h

@@ -5861,7 +5861,7 @@ VARCACHE_PREF(
 #undef PREF_VALUE
 
 #if defined(XP_WIN)
-# if defined(_ARM64_) || defined(__MINGW32__)
+# if defined(_ARM64_)
 #  define PREF_VALUE false
 # else
 #  define PREF_VALUE true

modules/libpref/init/all.js

@@ -491,7 +491,7 @@ pref("media.cubeb.sandbox", false);
 pref("media.audiograph.single_thread.enabled", false);
 
 #ifdef MOZ_AV1
-#if defined(XP_WIN) && !defined(_ARM64_) && !defined(__MINGW32__)
+#if defined(XP_WIN) && !defined(_ARM64_)
 pref("media.av1.enabled", true);
 pref("media.av1.use-dav1d", true);
 #elif defined(XP_MACOSX)