[WebAssembly][lld] Fix for static linking of PIC code

When statically linking PIC code we create an internalized __memory_base
so that memory-base-relative relocation work correctly.  The value of
this global should be zero, and not the globalBase since the globalBase
offset is already taken into account by getVirtualAddress.

Fixes: emscripten-core/emscripten#9013

Differential Revision: https://reviews.llvm.org/D69600

lld/test/wasm/pic-static.ll

@@ -118,4 +118,4 @@ entry:
 ; CHECK-NEXT:         Mutable:         false
 ; CHECK-NEXT:         InitExpr:
 ; CHECK-NEXT:           Opcode:          I32_CONST
-; CHECK-NEXT:           Value:           1024
+; CHECK-NEXT:           Value:           0

lld/wasm/Writer.cpp

@@ -226,8 +226,6 @@ void Writer::layoutMemory() {
 
   if (WasmSym::globalBase)
     WasmSym::globalBase->setVirtualAddress(memoryPtr);
-  if (WasmSym::definedMemoryBase)
-    WasmSym::definedMemoryBase->setVirtualAddress(memoryPtr);
 
   uint32_t dataStart = memoryPtr;