cmd/go: copy FFLAGS from build.Package

Fixes #18975.

Change-Id: I60dfb299233ecfed4b2da93750ea84e7921f1fbb
Reviewed-on: https://go-review.googlesource.com/36482
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/go/go_test.go

@@ -3777,3 +3777,24 @@ func TestA(t *testing.T) {}`)
 	tg.grepStdout("pkgs$", "expected package not listed")
 	tg.grepStdout("pkgs/a", "expected package not listed")
 }
+
+// Issue 18975.
+func TestFFLAGS(t *testing.T) {
+	if !canCgo {
+		t.Skip("skipping because cgo not enabled")
+	}
+
+	tg := testgo(t)
+	defer tg.cleanup()
+	tg.parallel()
+
+	tg.tempFile("p/src/p/main.go", `package main
+		// #cgo FFLAGS: -no-such-fortran-flag
+		import "C"
+		func main() {}
+	`)
+	tg.tempFile("p/src/p/a.f", `! comment`)
+	tg.setenv("GOPATH", tg.path("p"))
+	tg.runFail("build", "-x", "p")
+	tg.grepStderr("no-such-fortran-flag", `missing expected "-no-such-fortran-flag"`)
+}

src/cmd/go/internal/load/pkg.go

@@ -184,6 +184,7 @@ func (p *Package) copyBuild(pp *build.Package) {
 	p.CgoCFLAGS = pp.CgoCFLAGS
 	p.CgoCPPFLAGS = pp.CgoCPPFLAGS
 	p.CgoCXXFLAGS = pp.CgoCXXFLAGS
+	p.CgoFFLAGS = pp.CgoFFLAGS
 	p.CgoLDFLAGS = pp.CgoLDFLAGS
 	p.CgoPkgConfig = pp.CgoPkgConfig
 	// We modify p.Imports in place, so make copy now.