[WebAssembly] MC: Add compile-twice test and fix corresponding bug

Differential Revision: https://reviews.llvm.org/D47398

llvm-svn: 333494
diff --git a/llvm/lib/MC/WasmObjectWriter.cpp b/llvm/lib/MC/WasmObjectWriter.cpp
index a9ff7be..5a979d3 100644
--- a/llvm/lib/MC/WasmObjectWriter.cpp
+++ b/llvm/lib/MC/WasmObjectWriter.cpp
@@ -270,9 +270,9 @@
     Globals.clear();
     DataSegments.clear();
     SectionFunctions.clear();
-    MCObjectWriter::reset();
     NumFunctionImports = 0;
     NumGlobalImports = 0;
+    MCObjectWriter::reset();
   }
 
   void writeHeader(const MCAssembler &Asm);