Reapply "DWARF and unwind support for AOT assembly output."

runtime/vm/assembler_arm.cc

Index: runtime/vm/assembler_arm.cc
diff --git a/runtime/vm/assembler_arm.cc b/runtime/vm/assembler_arm.cc
index 5d5e4286b8f89ebd4e5d711b507a241c682228cc..11ed95d56e0dcbde4aaef754e4b6f432129d9759 100644
--- a/runtime/vm/assembler_arm.cc
+++ b/runtime/vm/assembler_arm.cc
@@ -3193,7 +3193,9 @@ void Assembler::EnterFrame(RegList regs, intptr_t frame_size) {
     // Set FP to the saved previous FP.
     add(FP, SP, Operand(4 * NumRegsBelowFP(regs)));
   }
-  AddImmediate(SP, -frame_size);
+  if (frame_size != 0) {
+    AddImmediate(SP, -frame_size);
+  }
 }