This replaces the link meta attributes with a pkgid attribute and uses a hash
of this as the crate hash. This makes the crate hash computable by things
other than the Rust compiler. It also switches the hash function ot SHA1 since
that is much more likely to be available in shell, Python, etc than SipHash.
Fixes#10188, #8523.
LLVM code generator emits the ".file filename" directive for ELF
backends. Value of the "filename" is set as the LLVM module identifier.
Due to a LLVM MC bug[1], LLVM crashes if the module identifer is same as
other symbols such as a function name in the module.
This patch adds a ".rc" suffix (means crates) to LLVM module identifier
to workaround the bug.
Fixes issue #1251.
1. http://llvm.org/bugs/show_bug.cgi?id=11479
