[LLD][ELF] Support OVERLAY NOCROSSREFS (#133807)

This allows NOCROSSREFS to be specified in OVERLAY linker script
descriptions. This is a particularly useful part of the OVERLAY syntax,
since it's very rarely possible for one overlay section to sensibly
reference another.

Closes #128790

lld/ELF/ScriptParser.cpp

@@ -565,6 +565,7 @@ SmallVector<SectionCommand *, 0> ScriptParser::readOverlay() {
     addrExpr = readExpr();
     expect(":");
   }
+  bool noCrossRefs = consume("NOCROSSREFS");
   Expr lmaExpr = consume("AT") ? readParenExpr() : Expr{};
   expect("{");
 
@@ -595,6 +596,12 @@ SmallVector<SectionCommand *, 0> ScriptParser::readOverlay() {
       static_cast<OutputDesc *>(od)->osec.memoryRegionName =
           std::string(regionName);
   }
+  if (noCrossRefs) {
+    NoCrossRefCommand cmd;
+    for (SectionCommand *od : v)
+      cmd.outputSections.push_back(static_cast<OutputDesc *>(od)->osec.name);
+    ctx.script->noCrossRefs.push_back(std::move(cmd));
+  }
 
   // According to the specification, at the end of the overlay, the location
   // counter should be equal to the overlay base address plus size of the