cmd/gomobile: add -work flag.

In order to make the artifacts of go build command preserved under WORK
directory, this change modifies TMPDIR (TEMP/TMP for windows)
environment variables to point to gomobile's tmpdir if -work flag is set.

> gomobile init -work
WORK=/gopath/pkg/gomobile/work-276689736

> ls /gopath/pkg/gomobile/work-276689736
README			go-build823903592	openal
android-ndk-r10e	go-build858075903
go-build365743399	go-build921886344

> gomobile build -work golang.org/x/mobile/example/basic
WORK=/tmp/gomobile-work-863381843

> ls /tmp/gomobile-work-863381843
go-build102034516	libbasic.so

> gomobile bind -work github.com/hyangah/ivy
WORK=/tmp/gomobile-work-355100962

> ls /tmp/gomobile-work-355100962
android			go-build284034365	javac-output
androidlib		go_ivy

Change-Id: I2f467e0063bc1c8b8c636a8cd6d100e86a99a91a
Reviewed-on: https://go-review.googlesource.com/12720
Reviewed-by: David Crawshaw <crawshaw@golang.org>

cmd/gomobile/bind.go

@@ -56,8 +56,8 @@ installed. Support is not complete.
 
 The -v flag provides verbose output, including the list of packages built.
 
-The build flags -a, -i, -n, -x, -gcflags, -ldflags, and -tags are shared
+The build flags -a, -i, -n, -x, -gcflags, -ldflags, -tags, and -work
-with the build command. For documentation, see 'go help build'.
+are shared with the build command. For documentation, see 'go help build'.
 `,
 }
 

cmd/gomobile/bind_androidapp.go

@@ -265,7 +265,6 @@ func buildJar(w io.Writer, srcDir string) error {
 			return err
 		}
 	}
-	defer removeAll(dst)
 
 	apiPath, err := androidAPIPath()
 	if err != nil {

cmd/gomobile/build.go

@@ -51,8 +51,8 @@ output file name depends on the package built.
 
 The -v flag provides verbose output, including the list of packages built.
 
-The build flags -a, -i, -n, -x, -gcflags, -ldflags, and -tags are shared
+The build flags -a, -i, -n, -x, -gcflags, -ldflags, -tags, and -work are
-with the build command. For documentation, see 'go help build'.
+shared with the build command. For documentation, see 'go help build'.
 `,
 }
 
@@ -208,6 +208,7 @@ var (
 	buildGcflags string // -gcflags
 	buildLdflags string // -ldflags
 	buildTarget  string // -target
+	buildWork    bool   // -work
 )
 
 func addBuildFlags(cmd *command) {
@@ -221,10 +222,11 @@ func addBuildFlags(cmd *command) {
 	cmd.flag.Var((*stringsFlag)(&ctx.BuildTags), "tags", "")
 }
 
-func addBuildFlagsNVX(cmd *command) {
+func addBuildFlagsNVXWork(cmd *command) {
 	cmd.flag.BoolVar(&buildN, "n", false, "")
 	cmd.flag.BoolVar(&buildV, "v", false, "")
 	cmd.flag.BoolVar(&buildX, "x", false, "")
+	cmd.flag.BoolVar(&buildWork, "work", false, "")
 }
 
 type binInfo struct {
@@ -234,15 +236,15 @@ type binInfo struct {
 
 func init() {
 	addBuildFlags(cmdBuild)
-	addBuildFlagsNVX(cmdBuild)
+	addBuildFlagsNVXWork(cmdBuild)
 
 	addBuildFlags(cmdInstall)
-	addBuildFlagsNVX(cmdInstall)
+	addBuildFlagsNVXWork(cmdInstall)
 
-	addBuildFlagsNVX(cmdInit)
+	addBuildFlagsNVXWork(cmdInit)
 
 	addBuildFlags(cmdBind)
-	addBuildFlagsNVX(cmdBind)
+	addBuildFlagsNVXWork(cmdBind)
 }
 
 func goBuild(src string, env []string, args ...string) error {
@@ -270,6 +272,9 @@ func goBuild(src string, env []string, args ...string) error {
 	if buildLdflags != "" {
 		cmd.Args = append(cmd.Args, "-ldflags", buildLdflags)
 	}
+	if buildWork {
+		cmd.Args = append(cmd.Args, "-work")
+	}
 	cmd.Args = append(cmd.Args, args...)
 	cmd.Args = append(cmd.Args, src)
 	cmd.Env = append([]string{}, env...)

cmd/gomobile/env.go

@@ -56,7 +56,13 @@ func buildEnvInit() (cleanup func(), err error) {
 		return nil, errors.New("toolchain not installed, run `gomobile init`")
 	}
 
-	cleanupFn := func() { removeAll(tmpdir) }
+	cleanupFn := func() {
+		if buildWork {
+			fmt.Printf("WORK=%s\n", tmpdir)
+			return
+		}
+		removeAll(tmpdir)
+	}
 	if buildN {
 		tmpdir = "$WORK"
 		cleanupFn = func() {}

cmd/gomobile/init.go

@@ -107,7 +107,13 @@ func runInit(cmd *command) error {
 	if buildX || buildN {
 		fmt.Fprintln(xout, "WORK="+tmpdir)
 	}
-	defer removeAll(tmpdir)
+	defer func() {
+		if buildWork {
+			fmt.Printf("WORK=%s\n", tmpdir)
+			return
+		}
+		removeAll(tmpdir)
+	}()
 
 	if err := fetchNDK(); err != nil {
 		return err
@@ -178,6 +184,9 @@ func installStd(env []string, args ...string) error {
 	if buildX {
 		cmd.Args = append(cmd.Args, "-x")
 	}
+	if buildWork {
+		cmd.Args = append(cmd.Args, "-work")
+	}
 	cmd.Args = append(cmd.Args, "std")
 	cmd.Env = append([]string{}, env...)
 	return runCmd(cmd)
@@ -536,6 +545,7 @@ func removeAll(path string) error {
 	if buildN {
 		return nil
 	}
+
 	// os.RemoveAll behaves differently in windows.
 	// http://golang.org/issues/9606
 	if goos == "windows" {
@@ -600,6 +610,15 @@ func runCmd(cmd *exec.Cmd) error {
 		cmd.Stderr = buf
 	}
 
+	if buildWork {
+		if goos == "windows" {
+			cmd.Env = append(cmd.Env, `TEMP=`+tmpdir)
+			cmd.Env = append(cmd.Env, `TMP=`+tmpdir)
+		} else {
+			cmd.Env = append(cmd.Env, `TMPDIR=`+tmpdir)
+		}
+	}
+
 	if !buildN {
 		cmd.Env = environ(cmd.Env)
 		if err := cmd.Run(); err != nil {

cmd/gomobile/install.go

@@ -21,7 +21,8 @@ attached mobile device.
 
 Only -target android is supported. The 'adb' tool must be on the PATH.
 
-The build flags -a, -i, -n, -x, and -tags are shared with the build command.
+The build flags -a, -i, -n, -x, -gcflags, -ldflags, -tags, and -work are
+shared with the build command.
 For documentation, see 'go help build'.
 `,
 }