Guard gcc_version in a safe condition.

gcc_version is only defined on Linux and thus we need to check for it before
using it on other platforms.

This should fix the following error:

gyp: name 'gcc_version' is not defined while evaluating condition 'gcc_version >= 48'

R=thakis@chromium.org

Review URL: https://codereview.chromium.org/14172021

git-svn-id: http://src.chromium.org/svn/trunk/deps/third_party/hunspell@196565 4ff67af0-8c30-449e-8e8b-ad334ec8d88c
1 file changed