[WebAssembly] make wasm-ld --verbose show data section startVA and name

[quantum]

Summary

Make wasm-ld --verbose show data section start virtual address and name
as well, instead of just showing the size. This makes it much easier to
track which global variable is in which address when used in conjunction
with --no-merge-data-sections.

[ruiu]

You might be interested in adding -Map option to lld/wasm. I found that option useful, as it prints out a layout information in a hierarchical manner. Here is an implementation for lld/ELF.

https://github.com/llvm-project/lld/blob/master/ELF/MapFile.cpp

[ruiu]

By the way this LGTM

lld/trunk/wasm/OutputSections.cpp

if (Config->Pic) {
       InitExpr.Value.Int32 = Segment->StartVA;
     }
     writeInitExpr(OS, InitExpr);
     writeUleb128(OS, Segment->Size, "segment size");
     OS.flush();
 
     Segment->SectionOffset = BodySize;
     BodySize += Segment->Header.size() + Segment->Size;
-    log("Data segment: size=" + Twine(Segment->Size));
+    log("Data segment: size=" + Twine(Segment->Size) + ", startVA=" +
+        Twine::utohexstr(Segment->StartVA) + ", name=" + Segment->Name);
 
     for (InputSegment *InputSeg : Segment->InputSegments)
       InputSeg->OutputOffset = Segment->SectionOffset + Segment->Header.size() +
                                InputSeg->OutputSegmentOffset;
   }
 
   createHeader(BodySize);
 }