bionic: add support for non-NEON memcpy() on NEON SoCs

Some SoCs that support NEON nevertheless perform better with a non-NEON than a
NEON memcpy().  This patch adds build variable ARCH_ARM_USE_NON_NEON_MEMCPY,
which can be set in BoardConfig.mk.  When ARCH_ARM_USE_NON_NEON_MEMCPY is
defined, we compile in the non-NEON optimized memcpy() even if the SoC supports
NEON.

Change-Id: Ia0e5bee6bad5880ffc5ff8f34a1382d567546cf9
diff --git a/libc/Android.mk b/libc/Android.mk
index dab6523..a403146 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -478,6 +478,9 @@
   ifeq ($(ARCH_ARM_HAVE_TLS_REGISTER),true)
     libc_common_cflags += -DHAVE_ARM_TLS_REGISTER
   endif
+  ifeq ($(ARCH_ARM_USE_NON_NEON_MEMCPY),true)
+    libc_common_cflags += -DARCH_ARM_USE_NON_NEON_MEMCPY
+  endif
 else # !arm
   ifeq ($(TARGET_ARCH),x86)
     libc_crt_target_cflags :=