The name of the ZCU object file emitted by the LLVM backend has been
changed in this branch from e.g. `foo.obj` to `foo_zcu.obj`. This is to
avoid name clashes. This commit just updates the stack trace tests which
started failing on windows because of the object name change.
Allows the stack trace tests to be additionally compiled and run with
`.use_llvm = false, .use_lld = false` depending on the host target. This
is currently enabled for x86_64 targets emitting ELF.
Self-hosted backends emit slightly different DWARF info to the LLVM
backend, so the checking logic (and the tests themselves) had to be
tweaked slightly to support both backends at once.
* RunStep: ability to set stdin
* RunStep: ability to capture stdout and stderr as a FileSource
* RunStep: add setName method
* RunStep: hash the stdio checks
