backend=auto (now the default if backend is omitted) means to let the compiler
pick whatever backend it wants as the default. This is important for platforms
where we don't yet have a self-hosted backend, such as loongarch64.
Also purge a bunch of redundant target=native.
/home/alexrp/.cache/zig/b/18236e302af25e3fb99bc6a232ddc447/builtin.zig:6:5: error: TODO (SPIR-V): Implement unsigned composite int type of 64 bits
pub const zig_backend = std.builtin.CompilerBackend.stage2_spirv64;
~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Under some architecture/operating system combinations it is forbidden
to return a pointer from a merge, as these pointers must point to a
location at compile time. This adds a check for those cases when
returning a pointer from a block merge.
