cmd/gomobile: enable bitcode

Add -fembed-bitcode to the host compiler and linker to instruct it
to add bitcode to object files.

Updates golang/go#22395

Change-Id: Ie0297079f27c9b5b8ea55e0a36067dc768342986
Reviewed-on: https://go-review.googlesource.com/c/mobile/+/168062
Run-TryBot: Elias Naur <mail@eliasnaur.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Author: eliasnaur

cmd/gomobile/bind_test.go

@@ -188,7 +188,7 @@ jar c -C $WORK/javac-output .
 var bindIOSTmpl = template.Must(template.New("output").Parse(`GOMOBILE={{.GOPATH}}/pkg/gomobile
 WORK=$WORK
 GOOS=darwin CGO_ENABLED=1 gobind -lang=go,objc -outdir=$WORK -tags=ios{{if .Prefix}} -prefix={{.Prefix}}{{end}} golang.org/x/mobile/asset
-GOARM=7 GOOS=darwin GOARCH=arm CC=iphoneos-clang CXX=iphoneos-clang++ CGO_CFLAGS=-isysroot=iphoneos -miphoneos-version-min=7.0 -arch armv7 CGO_CXXFLAGS=-isysroot=iphoneos -miphoneos-version-min=7.0 -arch armv7 CGO_LDFLAGS=-isysroot=iphoneos -miphoneos-version-min=7.0 -arch armv7 CGO_ENABLED=1 GOPATH=$WORK:$GOPATH go build -tags ios -x -buildmode=c-archive -o $WORK/asset-arm.a gobind
+GOARM=7 GOOS=darwin GOARCH=arm CC=iphoneos-clang CXX=iphoneos-clang++ CGO_CFLAGS=-isysroot=iphoneos -miphoneos-version-min=7.0 -fembed-bitcode -arch armv7 CGO_CXXFLAGS=-isysroot=iphoneos -miphoneos-version-min=7.0 -fembed-bitcode -arch armv7 CGO_LDFLAGS=-isysroot=iphoneos -miphoneos-version-min=7.0 -fembed-bitcode -arch armv7 CGO_ENABLED=1 GOPATH=$WORK:$GOPATH GO111MODULE=off go build -tags ios -x -buildmode=c-archive -o $WORK/asset-arm.a gobind
 rm -r -f "Asset.framework"
 mkdir -p Asset.framework/Versions/A/Headers
 ln -s A Asset.framework/Versions/Current

cmd/gomobile/build_darwin_test.go

@@ -94,10 +94,10 @@ mkdir -p $WORK/main
 echo "{{template "infoplist" .Xinfo}}" > $WORK/main/Info.plist
 mkdir -p $WORK/main/Images.xcassets/AppIcon.appiconset
 echo "{{.Xcontents}}" > $WORK/main/Images.xcassets/AppIcon.appiconset/Contents.json{{end}}
-GOARM=7 GOOS=darwin GOARCH=arm CC=iphoneos-clang CXX=iphoneos-clang++ CGO_CFLAGS=-isysroot=iphoneos -miphoneos-version-min=7.0 -arch armv7 CGO_CXXFLAGS=-isysroot=iphoneos -miphoneos-version-min=7.0 -arch armv7 CGO_LDFLAGS=-isysroot=iphoneos -miphoneos-version-min=7.0 -arch armv7 CGO_ENABLED=1 go build -tags tag1 ios -x {{if .Main}}-ldflags=-w -o=$WORK/arm {{end}}{{.Pkg}}
-GOOS=darwin GOARCH=arm64 CC=iphoneos-clang CXX=iphoneos-clang++ CGO_CFLAGS=-isysroot=iphoneos -miphoneos-version-min=7.0 -arch arm64 CGO_CXXFLAGS=-isysroot=iphoneos -miphoneos-version-min=7.0 -arch arm64 CGO_LDFLAGS=-isysroot=iphoneos -miphoneos-version-min=7.0 -arch arm64 CGO_ENABLED=1 go build -tags tag1 ios -x {{if .Main}}-ldflags=-w -o=$WORK/arm64 {{end}}{{.Pkg}}
-GOOS=darwin GOARCH=386 CC=iphonesimulator-clang CXX=iphonesimulator-clang++ CGO_CFLAGS=-isysroot=iphonesimulator -mios-simulator-version-min=7.0 -arch i386 CGO_CXXFLAGS=-isysroot=iphonesimulator -mios-simulator-version-min=7.0 -arch i386 CGO_LDFLAGS=-isysroot=iphonesimulator -mios-simulator-version-min=7.0 -arch i386 CGO_ENABLED=1 go build -tags tag1 ios -x {{if .Main}}-ldflags=-w -o=$WORK/386 {{end}}{{.Pkg}}
-GOOS=darwin GOARCH=amd64 CC=iphonesimulator-clang CXX=iphonesimulator-clang++ CGO_CFLAGS=-isysroot=iphonesimulator -mios-simulator-version-min=7.0 -arch x86_64 CGO_CXXFLAGS=-isysroot=iphonesimulator -mios-simulator-version-min=7.0 -arch x86_64 CGO_LDFLAGS=-isysroot=iphonesimulator -mios-simulator-version-min=7.0 -arch x86_64 CGO_ENABLED=1 go build -tags tag1 ios -x {{if .Main}}-ldflags=-w -o=$WORK/amd64 {{end}}{{.Pkg}}{{if .Main}}
+GOARM=7 GOOS=darwin GOARCH=arm CC=iphoneos-clang CXX=iphoneos-clang++ CGO_CFLAGS=-isysroot=iphoneos -miphoneos-version-min=7.0 -fembed-bitcode -arch armv7 CGO_CXXFLAGS=-isysroot=iphoneos -miphoneos-version-min=7.0 -fembed-bitcode -arch armv7 CGO_LDFLAGS=-isysroot=iphoneos -miphoneos-version-min=7.0 -fembed-bitcode -arch armv7 CGO_ENABLED=1 GO111MODULE=off go build -tags tag1 ios -x {{if .Main}}-ldflags=-w -o=$WORK/arm {{end}}{{.Pkg}}
+GOOS=darwin GOARCH=arm64 CC=iphoneos-clang CXX=iphoneos-clang++ CGO_CFLAGS=-isysroot=iphoneos -miphoneos-version-min=7.0 -fembed-bitcode -arch arm64 CGO_CXXFLAGS=-isysroot=iphoneos -miphoneos-version-min=7.0 -fembed-bitcode -arch arm64 CGO_LDFLAGS=-isysroot=iphoneos -miphoneos-version-min=7.0 -fembed-bitcode -arch arm64 CGO_ENABLED=1 GO111MODULE=off go build -tags tag1 ios -x {{if .Main}}-ldflags=-w -o=$WORK/arm64 {{end}}{{.Pkg}}
+GOOS=darwin GOARCH=386 CC=iphonesimulator-clang CXX=iphonesimulator-clang++ CGO_CFLAGS=-isysroot=iphonesimulator -mios-simulator-version-min=7.0 -fembed-bitcode -arch i386 CGO_CXXFLAGS=-isysroot=iphonesimulator -mios-simulator-version-min=7.0 -fembed-bitcode -arch i386 CGO_LDFLAGS=-isysroot=iphonesimulator -mios-simulator-version-min=7.0 -fembed-bitcode -arch i386 CGO_ENABLED=1 GO111MODULE=off go build -tags tag1 ios -x {{if .Main}}-ldflags=-w -o=$WORK/386 {{end}}{{.Pkg}}
+GOOS=darwin GOARCH=amd64 CC=iphonesimulator-clang CXX=iphonesimulator-clang++ CGO_CFLAGS=-isysroot=iphonesimulator -mios-simulator-version-min=7.0 -fembed-bitcode -arch x86_64 CGO_CXXFLAGS=-isysroot=iphonesimulator -mios-simulator-version-min=7.0 -fembed-bitcode -arch x86_64 CGO_LDFLAGS=-isysroot=iphonesimulator -mios-simulator-version-min=7.0 -fembed-bitcode -arch x86_64 CGO_ENABLED=1 GO111MODULE=off go build -tags tag1 ios -x {{if .Main}}-ldflags=-w -o=$WORK/amd64 {{end}}{{.Pkg}}{{if .Main}}
 xcrun lipo -o $WORK/main/main -create $WORK/arm $WORK/arm64 $WORK/386 $WORK/amd64
 mkdir -p $WORK/main/assets
 xcrun xcodebuild -configuration Release -project $WORK/main.xcodeproj -allowProvisioningUpdates DEVELOPMENT_TEAM={{.TeamID}}

cmd/gomobile/env.go

@@ -128,6 +128,7 @@ func envInit() (err error) {
 		default:
 			panic(fmt.Errorf("unknown GOARCH: %q", arch))
 		}
+		cflags += " -fembed-bitcode"
 		if err != nil {
 			return err
 		}