Generate gnu hash for arm only

Fixes build failure caused by:
https://android-review.googlesource.com/#/c/139660

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: I9a7966eebfd1ef0a587a20b71faefde38e84ab62
diff --git a/libc/Android.mk b/libc/Android.mk
index d0ef772..293b70e 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -1326,7 +1326,7 @@
 LOCAL_CPPFLAGS := $(libc_common_cppflags)
 
 # TODO: This is to work around b/19059885. Remove after root cause is fixed
-LOCAL_LDFLAGS := -Wl,--hash-style=both
+LOCAL_LDFLAGS_arm := -Wl,--hash-style=both
 
 LOCAL_C_INCLUDES := $(libc_common_c_includes)
 LOCAL_SRC_FILES := \
@@ -1480,7 +1480,7 @@
 LOCAL_CPPFLAGS := $(libc_common_cppflags)
 
 # TODO: This is to work around b/19059885. Remove after root cause is fixed
-LOCAL_LDFLAGS := -Wl,--hash-style=both
+LOCAL_LDFLAGS_arm := -Wl,--hash-style=both
 
 LOCAL_SRC_FILES := $(libstdcxx_common_src_files)
 LOCAL_MODULE:= libstdc++