Revert 73304 (broke clang/linux) - Use early expansion for debug_optimize and release_optimize
Revert 73304 (broke clang/linux) - Use early expansion for debug_optimize and release_optimize

This fixes a bug when these flags are not overriden from ~/.gyp/include.gypi
which is the way they should be set for Valgrind builds
(see http://dev.chromium.org/developers/how-tos/using-valgrind )

BUG=70107
TEST=gclient runhooks --force && grep "\-O" base/base.target.mk
Review URL: http://codereview.chromium.org/6267004

TBR=timurrrr@chromium.org
Review URL: http://codereview.chromium.org/6334026

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@73329 0039d316-1c4b-4281-b951-d872f2087c98

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