cmd/gomobile: do not pass -i to 'go install' command

Fixes golang/go#13407

Also updates bind test.

'gomobile bind' currently runs 'go install' first and generates code
from the compiled object. This makes the -i option unnecessary.
Updated the bind command doc not to mention the -i option.

The use of -i option from Android Studio GoBind plugin will be removed
in a separate CL.

Change-Id: Ie48c00874219adb5169e01d3ba61930728cf2314
Reviewed-on: https://go-review.googlesource.com/17253
Reviewed-by: David Crawshaw <crawshaw@golang.org>

cmd/gomobile/bind.go

@@ -56,7 +56,7 @@ are prefixed with 'Go' unless the -prefix flag is provided.
 
 The -v flag provides verbose output, including the list of packages built.
 
-The build flags -a, -i, -n, -x, -gcflags, -ldflags, -tags, and -work
+The build flags -a, -n, -x, -gcflags, -ldflags, -tags, and -work
 are shared with the build command. For documentation, see 'go help build'.
 `,
 }

cmd/gomobile/bind_test.go

@@ -101,6 +101,11 @@ func TestBindAndroid(t *testing.T) {
 
 var bindAndroidTmpl = template.Must(template.New("output").Parse(`GOMOBILE={{.GOPATH}}/pkg/gomobile
 WORK=$WORK
+GOOS=android GOARCH=arm GOARM=7 CC=$GOMOBILE/android-ndk-r10e/arm/bin/arm-linux-androideabi-gcc CXX=$GOMOBILE/android-ndk-r10e/arm/bin/arm-linux-androideabi-g++ CGO_ENABLED=1 go install -p={{.NumCPU}} -pkgdir=$GOMOBILE/pkg_android_arm -tags="" -x golang.org/x/mobile/asset
+rm -r -f "$WORK/fakegopath"
+mkdir -p $WORK/fakegopath/pkg
+cp $GOMOBILE/pkg_android_arm/golang.org/x/mobile/asset.a $WORK/fakegopath/pkg/android_arm/golang.org/x/mobile/asset.a
+mkdir -p $WORK/fakegopath/pkg/android_arm/golang.org/x/mobile
 mkdir -p $WORK/go_asset
 gobind -lang=go -outdir=$WORK/go_asset golang.org/x/mobile/asset
 mkdir -p $WORK/androidlib

cmd/gomobile/build.go

@@ -268,7 +268,7 @@ func goCmd(subcmd string, srcs []string, env []string, args ...string) error {
 	if buildV {
 		cmd.Args = append(cmd.Args, "-v")
 	}
-	if buildI {
+	if subcmd != "install" && buildI {
 		cmd.Args = append(cmd.Args, "-i")
 	}
 	if buildX {