Fixed bug on IsEnvFlagTrue.
Fixed bug on IsEnvFlagTrue.

Due to the misuse of re.search, the function always returns false if
environment variable is set.

NOTRY=true

Review URL: https://codereview.chromium.org/184333002

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@12853 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client