gcc: Extend .gccrelocprefix section support to musl configs

musl includes were not using the relocatable prefix like glibc
counterpart, this will mean that musl SDKs will behave better and find
the headers in right install directories

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>