[dev.power64] runtime: move noasm_arm.goc to noasm.goc

LGTM=rsc
R=rsc, iant
CC=golang-codereviews
https://golang.org/cl/121590043

src/pkg/runtime/noasm_arm.goc → src/pkg/runtime/noasm.goc

@@ -5,6 +5,8 @@
 // Routines that are implemented in assembly in asm_{amd64,386}.s
 // but are implemented in C for arm.
 
+// +build arm power64 power64le
+
 package runtime
 #include "runtime.h"
 #include "../../cmd/ld/textflag.h"