linux-tools/perf: fix build for MIPS by using the right emulation on LD

Passing just the endianness flag to LD is not enough. We need to pass
the right emulation flag which will set everything for us, not only the
endianness.

Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>