Bring base/BUILD.gn up-to-date with build file changes.

R=scottmg@chromium.org
TBR=scottmg@chromium.org

Review URL: https://codereview.chromium.org/137533004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244780 0039d316-1c4b-4281-b951-d872f2087c98
Move GN's glib_cxx_debug flag onto the debug configuration.

Previously this was in a global config which also applied to the release build.

R=thakis@chromium.org
TBR=thakis@chromium.org

Review URL: https://codereview.chromium.org/137553002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244781 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 244781
Hook up ARM architecture flags to GN build.

This duplicates the ARM architecture logic from common.gypi.

R=scottmg@chromium.org
TBR=scottmg

Review URL: https://codereview.chromium.org/137493004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244782 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 244782