cmd/go: add more env variables to "go bug"

CL 31330 added more envvars to "go env".
This CL brings them to "go bug" as well.

Change-Id: Iae122072c8178007eda8b765aaa3f38c3c6e39a0
Reviewed-on: https://go-review.googlesource.com/32011
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/go/bug.go

@@ -39,7 +39,9 @@ func runBug(cmd *Command, args []string) {
 	fmt.Fprint(&buf, "#### System details\n\n")
 	fmt.Fprintln(&buf, "```")
 	fmt.Fprintf(&buf, "go version %s %s/%s\n", runtime.Version(), runtime.GOOS, runtime.GOARCH)
-	for _, e := range mkEnv() {
+	env := mkEnv()
+	env = append(env, extraEnvVars()...)
+	for _, e := range env {
 		fmt.Fprintf(&buf, "%s=\"%s\"\n", e.name, e.value)
 	}
 	printOSDetails(&buf)

src/cmd/go/env.go

@@ -88,21 +88,24 @@ func findEnv(env []envVar, name string) string {
 	return ""
 }
 
-func runEnv(cmd *Command, args []string) {
-	env := mkEnv()
-	// Add these environment variables here so they do not leak
-	// into child processes.
+// extraEnvVars returns environment variables that should not leak into child processes.
+func extraEnvVars() []envVar {
 	var b builder
 	b.init()
 	cppflags, cflags, cxxflags, fflags, ldflags := b.cflags(&Package{})
-	env = append(env,
-		envVar{"PKG_CONFIG", b.pkgconfigCmd()},
-		envVar{"CGO_CFLAGS", strings.Join(cflags, " ")},
-		envVar{"CGO_CPPFLAGS", strings.Join(cppflags, " ")},
-		envVar{"CGO_CXXFLAGS", strings.Join(cxxflags, " ")},
-		envVar{"CGO_FFLAGS", strings.Join(fflags, " ")},
-		envVar{"CGO_LDFLAGS", strings.Join(ldflags, " ")},
-	)
+	return []envVar{
+		{"PKG_CONFIG", b.pkgconfigCmd()},
+		{"CGO_CFLAGS", strings.Join(cflags, " ")},
+		{"CGO_CPPFLAGS", strings.Join(cppflags, " ")},
+		{"CGO_CXXFLAGS", strings.Join(cxxflags, " ")},
+		{"CGO_FFLAGS", strings.Join(fflags, " ")},
+		{"CGO_LDFLAGS", strings.Join(ldflags, " ")},
+	}
+}
+
+func runEnv(cmd *Command, args []string) {
+	env := mkEnv()
+	env = append(env, extraEnvVars()...)
 	if len(args) > 0 {
 		for _, name := range args {
 			fmt.Printf("%s\n", findEnv(env, name))