Implement the "abort" stub in assembly for ARM.

So that we can always get the full stack trace regardless of gcc's handling
of the "noreturn" attribute associated with abort().

[cherry-picked from master]

BUG:6455193
Change-Id: I0102355f5bf20e636d3feab9d1424495f38e39e2
diff --git a/libc/Android.mk b/libc/Android.mk
index d158dbc..dab6523 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -350,6 +350,7 @@
 	arch-arm/bionic/__get_sp.S \
 	arch-arm/bionic/_exit_with_stack_teardown.S \
 	arch-arm/bionic/_setjmp.S \
+	arch-arm/bionic/abort_arm.S \
 	arch-arm/bionic/atomics_arm.c \
 	arch-arm/bionic/clone.S \
 	arch-arm/bionic/eabi.c \