Similar to -fprofile-generate=, add -fmemory-profile= which takes a
directory path. This is passed down to LLVM via a new module flag
metadata. LLVM in turn provides this name to the runtime via the new
Additionally, always pass a default filename (in $cwd if a directory
name is not specified vi the = form of the option). This is also
consistent with the behavior of the PGO instrumentation. Since the
memory profiles will generally be fairly large, it doesn't make sense to
dump them to stderr. Also, importantly, the memory profiles will
eventually be dumped in a compact binary format, which is another reason
why it does not make sense to send these to stderr by default.
Depends on D89086.