libgcc: Fix symlink handling in cross-arch multilib cases
The symlink being generated needs to match both the current arch (e.g. mips
or mips64) but also use the underlying TARGET_SYS without multilib extensions
to TARGET_VENDOR or extensions to TARGET_OS.
The way multilib changes TARGET_VENDOR meant this code did not have
a way of removing that change. The method of removing some TARGET_OS
suffixes was also not working.
By using immediate expansion to run this code, we can run before the
multilib code changes it and get the original values.
We then use the *current* TARGET_ARCH value in case this does get changed
by the multilib since we need to point at the right compiler (32 bit one
for 32 bit code).
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
