This reverts commit 64effa9a71.
It turns out that the LLD handling of the TLS data structures
("_tls_used" and "_tls_index") needs more work, causing the
arm64ec side of arm64x binaries to not get them hooked up properly.
Extend the aarch64-w64-mingw32 prefix to provide ARM64EC libraries
alongside standard AArch64 libraries, replacing the separate
arm64ec-w64-mingw32 prefix. This aligns with how MSVC distributes
ARM64EC libraries and enables the linker to process both targets
simultaneously into a single hybrid binary.
This extensively utilizes LLVM's -marm64x option, compiling both
targets in a single compiler invocation to produce hybrid object
files (unlike MSVC tools, which require separate compilation passes).
This matches what is done in build-all.sh for the PGO step; this
removes rather large (~50 MB) libraries that mostly are needed
for compiling for the host unix platforms. (On Linux it's needed
if building with profiling, on macOS it's needed for the builtin
functions for platform version availability too.)
Martin Storsjö