superh port
make the x32 port use the correct ld-musl-x32.path filename

previously it was wrongly using the x86_64 one, precluding having both
x32 and x86_64 libs present on the same system.
fixup general __syscall breakage introduced in x32 port

the reordering of headers caused some risc archs to not see
the __syscall definition anymore.
this caused build errors on mips with any compiler,
and on arm and microblaze with clang.

we now define it locally just like the powerpc port does.