libunwind: fix build with aarch64

libunwind: fix build with aarch64

Referred to RP's fix for x86 and x86-64:
34d517a5626ce2465f776367349bd9e66bf8ed1f
libunwind: Build with gold to avoid build failures

Fixed:
aarch64-poky-linux/4.9.2/ld: copy reloc against protected `_Uaarch64_local_addr_space' is invalid
aarch64-poky-linux/4.9.2/ld: failed to set dynamic section sizes: Bad value
aarch64-poky-linux/4.9.2/ld: copy reloc against protected `_Uaarch64_local_addr_space' is invalid
aarch64-poky-linux/4.9.2/ld: failed to set dynamic section sizes: Bad value
| collect2: error: ld returned 1 exit status

(From OE-Core rev: 31d84f67f74b31b479409cfa446b14ac67bb3707)

Signed-off-by: Robert Yang <liezhi.yang@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>