[lld][WebAssembly] Don't emit names for data segments that we omit

[sbc100]

Summary

Followup to https://reviews.llvm.org/D92909

[tlively]

Aha, that seems important!

lld/test/wasm/bss-only.s

 # CHECK-NEXT:   - Type:            EXPORT
 # CHECK-NEXT:     Exports:
 # CHECK-NEXT:       - Name:            memory
 # CHECK-NEXT:         Kind:            MEMORY
 # CHECK-NEXT:         Index:           0
 # CHECK-NEXT:       - Name:            __data_end
 # CHECK-NEXT:         Kind:            GLOBAL
 # CHECK-NEXT:         Index:           1
+
+# CHECK-NOT: DataSegmentNames:

lld/wasm/SyntheticSections.cpp

unsigned NameSection::numNamedGlobals() const {
   numNames += out.globalSec->internalGotSymbols.size();
   return numNames;
 }
 
 unsigned NameSection::numNamedDataSegments() const {
   unsigned numNames = 0;
 
   for (const OutputSegment *s : segments)
-    if (!s->name.empty())
+    if (!s->name.empty() && !s->isBss)
       ++numNames;
 
   return numNames;
 }
 
 // Create the custom "name" section containing debug symbol names.
 void NameSection::writeBody() {
   unsigned count = numNamedFunctions();
void NameSection::writeBody() {
   }
 
   count = numNamedDataSegments();
   if (count) {
     SubSection sub(WASM_NAMES_DATA_SEGMENT);
     writeUleb128(sub.os, count, "name count");
 
     for (OutputSegment *s : segments) {
+      if (!s->name.empty() && !s->isBss) {
         writeUleb128(sub.os, s->index, "global index");
         writeStr(sub.os, s->name, "segment name");
       }
+    }
 
     sub.writeTo(bodyOutputStream);
   }
 }
 
 void ProducersSection::addInfo(const WasmProducerInfo &info) {
   for (auto &producers :
        {std::make_pair(&info.Languages, &languages),