Fixed spelling mistake of goma_dir_env.
Fixed spelling mistake of goma_dir_env.

If $GOMA_DIR is used, the code hit the spelling mistake and raised a runtime
error.  However, the error is hidden by try-except.

BUG=340483

Review URL: https://codereview.chromium.org/152863003

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@12704 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

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