adapt build of arm memcpy asm not to use .sub files

this depends on commit 9f5eb77992, which
made it possible to use a .c file for arch-specific replacements, and on
commit 2f853dd6b9, the out-of-tree build
support, which made it so that src/*/$(ARCH)/* 'replacement' files get
used even if they don't match the base name of a .c file in the parent
directory.

src/string/arm/memcpy.c

@@ -0,0 +1,3 @@
+#if __ARMEB__
+#include "../memcpy.c"
+#endif

src/string/arm/memcpy_le.S

@@ -1,3 +1,5 @@
+#ifndef __ARMEB__
+
 /*
  * Copyright (C) 2008 The Android Open Source Project
  * All rights reserved.
@@ -377,3 +379,5 @@ copy_last_3_and_return:
 	add     sp,  sp, #28
 	ldmfd   sp!, {r0, r4, lr}
 	bx      lr
+
+#endif

src/string/armel/memcpy.sub

@@ -1 +0,0 @@
-memcpy.s

src/string/armhf/memcpy.sub

@@ -1 +0,0 @@
-../armel/memcpy.s