cmd/compile: don't generate DWARF info for static vars

Static data symbols are compiler generated, not user symbols. The
linker already does not include them in the final DWARF section.
Don't generate the DWARF info in the first place.

Change-Id: Id2ae36683bfc1ed60b9924b7305eae5e8aa14d80
Reviewed-on: https://go-review.googlesource.com/c/go/+/490817
Run-TryBot: Cherry Mui <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

src/cmd/compile/internal/gc/obj.go

@@ -195,7 +195,7 @@ func dumpGlobal(n *ir.Name) {
 	}
 	types.CalcSize(n.Type())
 	ggloblnod(n)
-	if n.CoverageCounter() || n.CoverageAuxVar() {
+	if n.CoverageCounter() || n.CoverageAuxVar() || n.Linksym().Static() {
 		return
 	}
 	base.Ctxt.DwarfGlobal(base.Ctxt.Pkgpath, types.TypeSymName(n.Type()), n.Linksym())