This matters for C files that are also built for Windows. Previously they'd
be compiled with -std=gnu99 for the host but [effectively] -std=gnu89 for
Windows.
Bug: http://b/32019064
Test: builds, and can build libcrypto_utils without a manual -std= line
Change-Id: I9c5cc7832220b5c3d6a007ff10d076e26fd8c75d