Make the unwinder build on thumbv6-m with the integrated assembler.

http://reviews.llvm.org/D7630


git-svn-id: https://llvm.org/svn/llvm-project/libcxxabi/trunk@229194 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/src/Unwind/UnwindRegistersSave.S b/src/Unwind/UnwindRegistersSave.S
index 3f7400f..aa437ca 100644
--- a/src/Unwind/UnwindRegistersSave.S
+++ b/src/Unwind/UnwindRegistersSave.S
@@ -316,7 +316,11 @@
   str lr, [r0, #56]
   str lr, [r0, #60]  @ store return address as pc
 #endif
+#if __ARM_ARCH_ISA_THUMB1 == 1
+  movs r0, #0        @ return UNW_ESUCCESS
+#else
   mov r0, #0         @ return UNW_ESUCCESS
+#endif
   JMP(lr)
 
 @