The make macros add these to the linker lines even if the default
compiler flags are being skipped.
This also allows us to add another runpath for test binaries, which are
currently being installed in:
<out>/host/linux-x86/nativetest[64]/<test>/<binary>
So they need to use ../../lib[64] as a rpath.
Change-Id: Ia7e954cdf63bc627a8f71d01c953530355c248ab