gnu-config will ignore the portion of a triple matching the regex
`e?abi.*$` when determining the validity of a triple. In other
words, `i386-linuxabichickenlips` is a valid triple.
This commit updates our parsing routines to match gnu-config.
I was recently surprised to discover that it is in fact possible to
shoehorn ABI flavors into nix doubles in a way which preserves their
property of being a (non-canonical) subset of the valid gnu-config
triples. This commit is required in order to exploit that discovery
to add automatic detection of ILP32 platforms (64-bit void*, 32-bit
int, like the Apple Watch and MIPS n32) to Nix.
20b62456f0