[MCJIT] Fix the ARM BR24 relocation in RuntimeDyldMachO.

We now (1) correctly decode the branch immediate, (2) modify the immediate to
corretly treat it as PC-rel, and (3) properly populate the stub entry.
Previously we had been doing each of these wrong.

<rdar://problem/17750739>

llvm-svn: 214285
diff --git a/llvm/lib/ExecutionEngine/RuntimeDyld/Targets/RuntimeDyldMachOAArch64.h b/llvm/lib/ExecutionEngine/RuntimeDyld/Targets/RuntimeDyldMachOAArch64.h
index 967b12f..ced85f3 100644
--- a/llvm/lib/ExecutionEngine/RuntimeDyld/Targets/RuntimeDyldMachOAArch64.h
+++ b/llvm/lib/ExecutionEngine/RuntimeDyld/Targets/RuntimeDyldMachOAArch64.h
@@ -276,7 +276,7 @@
 
     bool IsExtern = Obj.getPlainRelocationExternal(RelInfo);
     if (!IsExtern && RE.IsPCRel)
-      makeValueAddendPCRel(Value, ObjImg, RelI);
+      makeValueAddendPCRel(Value, ObjImg, RelI, 1 << RE.Size);
 
     RE.Addend = Value.Addend;