Update ffmpeg binaries directories to support variants based off the target architecture.

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index 78c62adb9515bf2b51e590ab737f67872df07ad1..23b51733cb71b4e338b0bf2b0faec6c0c786e184 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -35,6 +35,9 @@
       # builds).
       'buildtype%': 'Dev',
 
+      # The architecture that we're building on.
+      'target_arch%': 'ia32',
+
       # We do want to build Chromium with Breakpad support in certain
       # situations. I.e. for Chrome bot.
       'linux_chromium_breakpad%': 0,
@@ -44,6 +47,7 @@
     # variables sub-dict above, unless overridden.
     'branding%': '<(branding)',
     'buildtype%': '<(buildtype)',
+    'target_arch%': '<(target_arch)',
 
     # Override chromium_mac_pch and set it to 0 to suppress the use of
     # precompiled headers on the Mac.  Prefix header injection may still be
@@ -114,9 +118,6 @@
     # but that doesn't work as we'd like.
     'msvs_debug_link_incremental%': '2',
 
-    # The architecture that we're building on.
-    'target_arch%': 'ia32',
-
     # By default linux does not use views. To turn on views in Linux
     # set the variable GYP_DEFINES to "toolkit_views=1", or modify
     # ~/.gyp/include.gypi .