ld64 cannot handle BR26 reloc with non-zero addend. It incorrectly
thinks that non-zero addend for BR26 means the code is not PIC, but
those BR26 relocs should be fully resolved at link time.

Change-Id: I3b3f80791a1db4c2b7318f81a115972cd2237f01
Signed-off-by: Shenghou Ma <minux@golang.org>
Reviewed-on: https://go-review.googlesource.com/8780Reviewed-by: David Crawshaw <crawshaw@golang.org>