src: re-enable fast math on arm
Refs: https://github.com/nodejs/node/issues/1376 and https://github.com/nodejs/node/pull/1398 V8 fixed the issue in https://chromium.googlesource.com/v8/v8/+/81703350bbb9923d211fe5b79e90bd458b0916e2 V8-Bug: https://code.google.com/p/v8/issues/detail?id=4019
This PR is against the vee-eight-4.5
branch, which I rebased on master