Accept env variable CC

Remove hardcoded `gcc` value and allow usage of `CC` environment
variable to define override.
Whitespace

Whitespace inspector was here and didn't like this.
Avoid non-ASCII output of GCC cause host detection issues

Temporarely set `LC_ALL` variable to force ASCII (C) output when
checking GCC platform.

This is done to avoid non-standard builds that might contain extended
characters making mini_portile crash.

Closes #22