Remove WTF_COMPILER_SUPPORTS_EABI flag

Remove WTF_COMPILER_SUPPORTS_EABI flag as it is never used.

Review URL: https://codereview.chromium.org/137823007

git-svn-id: svn://svn.chromium.org/blink/trunk@166090 bbb929c8-8fbe-4397-9dbb-9b2b20218538