Clang does not accept `-x objective-c` with WebAssembly target and it
crashes with "Objective-C support is unimplemented for object file
format" for now. `-enable-objc-interop` can work without the objc
runtime support (which is indicated by `objc_interop` feature), so this
adds a new `objc_codegen` feature to require Objective-C support only
at compile-time.
Now that we're never relatively addressing an Objective-C class reference,
stop emitting them as file-local (by eliminating the \01l_ prefix). This
is both a minor optimization and also a way to ensure that things will
break more consistently if a problem remains.
In-place initialization means the class has a symbol we can reference
from the category, so there's nothing to do on the IRGen side.
For JIT mode, we just need to realize the class metadata by calling an
accessor instead of directly referencing the symbol though.
This adds the dllstorage annotations on the tests. This first pass gets
most of the IRGen tests passing on Windows (though has dependencies on
other changes). However, this allows for the changes to be merged more
easily as we cannot regress other platforms here.
This prevents the linker from trying to emit relative relocations to locally-defined public symbols into dynamic libraries, which gives ld.so heartache.
