Generate gnu hash for arm only

Fixes build failure caused by:
https://android-review.googlesource.com/#/c/139670/

As previously discussed [1], MIPS does not support GNU-style ELF hashes.

[1] https://android-review.googlesource.com/#/c/49282/2/tests/Android.mk

Change-Id: I8edb8a1595308db2ecd1bd6650a069b1224ae64f
1 file changed