[memprof] Export __memprof_default_options_str on Darwin (#128920)
The `-memprof-runtime-default-options` LLVM flag introduced in
https://github.com/llvm/llvm-project/pull/118874 creates the
`__memprof_default_options_str` symbol with `WeakAnyLinkage` on Darwin.
https://github.com/ellishg/llvm-project/blob/fa0202169af23419c4bcbf66eabd1beb6b6e8e34/llvm/lib/Transforms/Instrumentation/MemProfiler.cpp#L573-L576
This ensures Darwin passes `-exported_symbol
___memprof_default_options_str` to the linker so that the runtime
library has visibility into this symbol.
This will replace the earlier PR
https://github.com/llvm/llvm-project/pull/128615
llvm-project
d2c4d1ec - [memprof] Export __memprof_default_options_str on Darwin (#128920)
