Our infra team found this error when building DevKit with GCC 4.9.2. The binutils version is 2.25, and an *.xz doesn't exist on https://ftp.gnu.org/pub/gnu/binutils/. Hence, [Joseph](https://github.com/junyzheng) would like to submit a PR to update *.xz to *.gz.
We have confirmed that *.gz exists for all binutil version.
We have confirmed that *.gz exists for all binutil version.