cmd/go: don't collect package CGOLDFLAGS when using gccgo

They are already collected via cmd/cgo.

The gccgo_link_c test is tweaked to do real linking as with this
change the cgo ldflags are not fully reflected in go build -n output,
since they now only come from the built archive.

Fixes #60287

Change-Id: Id433435fe8aeb9571327bf936e52a37f400cef4c
Reviewed-on: https://go-review.googlesource.com/c/go/+/497117
Run-TryBot: Ian Lance Taylor <[email protected]>
Reviewed-by: Heschi Kreinick <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Auto-Submit: Ian Lance Taylor <[email protected]>
Reviewed-by: Bryan Mills <[email protected]>
Reviewed-by: Andrey Bokhanko <[email protected]>

Author: ianlancetaylor

src/cmd/go/internal/work/gccgo.go

@@ -386,16 +386,9 @@ func (tools gccgoToolchain) link(b *Builder, root *Action, out, importcfg string
 	}
 
 	for _, a := range allactions {
-		// Gather CgoLDFLAGS, but not from standard packages.
-		// The go tool can dig up runtime/cgo from GOROOT and
-		// think that it should use its CgoLDFLAGS, but gccgo
-		// doesn't use runtime/cgo.
 		if a.Package == nil {
 			continue
 		}
-		if !a.Package.Standard {
-			cgoldflags = append(cgoldflags, a.Package.CgoLDFLAGS...)
-		}
 		if len(a.Package.CgoFiles) > 0 {
 			usesCgo = true
 		}
@@ -425,9 +418,6 @@ func (tools gccgoToolchain) link(b *Builder, root *Action, out, importcfg string
 
 	ldflags = append(ldflags, cgoldflags...)
 	ldflags = append(ldflags, envList("CGO_LDFLAGS", "")...)
-	if root.Package != nil {
-		ldflags = append(ldflags, root.Package.CgoLDFLAGS...)
-	}
 	if cfg.Goos != "aix" {
 		ldflags = str.StringList("-Wl,-(", ldflags, "-Wl,-)")
 	}

src/cmd/go/testdata/script/gccgo_link_c.txt

@@ -4,8 +4,9 @@
 [!cgo] skip
 [!exec:gccgo] skip
 
-go build -n -compiler gccgo
+! go build -x -compiler gccgo
 stderr 'gccgo.*\-L [^ ]*alibpath \-lalib' # make sure that Go-inline "#cgo LDFLAGS:" ("-L alibpath -lalib") passed to gccgo linking stage
+! stderr 'gccgo.*-lalib.*-lalib' # make sure -lalib is only passed once
 
 -- go.mod --
 module m