test/link/glibc_compat: Add C test case for glibc versions

[rootbeer]

Add glibc_runtime_check.c: a simple test case that exercises glibc functions that might smoke out linking problems with Zig's C compiler. The build.zig compiles it against a variety of glibc versions.

Also mark the aarch64 glibc minimum version as 2.17 (the aarch64_be target was already marked). This is necessary because earlier versions of glibc do not support the aarch64 architecture.

Also document and test glibc v2.2.5 (from 2002) as the oldest working glibc target for C binaries. (Earlier versions fail with a raft of missing symbols.)