GCC 4.9

[tavianator]

I'd like to build a piece of software, but it requires GCC 4.9.0 or above for stdatomic.h. There are plenty of ways to work around this though so my question is mostly out of curiosity: is there a testing repo or something that I could install it from? The PKGBUILD on github is for version 4.9.1 but the repos only have 4.8.2. Thanks!