Use the new module structure rather the old SwiftShims header. This
is much cleaner and lets us include operating system headers to get
the relevant definitions where possible.
Add code to support ELF and DWARF, including decompression using
zlib, zstd and liblzma if those turn out to be required and available.
rdar://110261712
Mike and Max made various helpful suggestions, so I've added and updated
various comments and amended the code to cope with partial reads and
writes.
rdar://110261430
This also adds a function to demangle a symbol, and a way for the
backtracing code to report warning messages to the same place as
the main runtime.
I'd like to rename the _swift_isThunkFunction() SPI also, but we
can't do that until we've made the changes to the _Backtracing
library, so we'll do that there instead.
rdar://110261430
Some symbolication frameworks have a symbol cache; we probably don't want
to use that for test cases, to avoid running into problems where the cache
holds stale information.
rdar://105409147
We really, really shouldn't be running the external backtracer for setuid
binaries. It's just too dangerous.
So don't do that. And if someone tries to force us, emit a warning.
rdar://105391747
