For musl we need to be able to add a library to the end of the linker commandline.
Rework the wrapper code to be able to do this through a new variable.
(From OE-Core rev: dfff5a176765c0e8b212bf31081f80e79025fd1b)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>