Support for non-glibc versions of linux (musl, android)

[spocino]

check if a linux implementation uses glibc to decide whether to load "glibc.so.6" or "glibc.so"

[Z-snails]

Would it be easier/faster to try loading libc.so.6 first, then if that fails try libc.so (using with-exception-handler) - that way we don't need to spawn a child process.

[mattpolzin]

I think that suggestion makes sense to me too; I think we could go even further and avoid the runtime check or fallback entirely too since our goal in loading the dynamic library is not actually to build once and then run in multiple different environments so we ought to be able to determine which library to use at compile time.