x/mobile/cmd/gomobile: compile error on mac when using "crypto/x509" package

[siuying]

What version of Go are you using (go version)?

go1.10.3 darwin/amd64

Does this issue reproduce with the latest release?

yes

What operating system and processor architecture are you using (go env)?

darwin/amd64

What did you do?

Compile to iOS target on Mac, if import contains "crypto/x509", will result in compile error:

$ gomobile build -target=ios .
gomobile: go build . failed: exit status 2
# crypto/x509
clang: error: invalid argument '-mmacosx-version-min=10.6' not allowed with '-mios-simulator-version-min=6.1'
clang: warning: using sysroot for 'iPhoneSimulator' but targeting 'MacOSX' [-Wincompatible-sysroot]

To reproduce the error, create a file hello.go:

hello.go

package hello

import (
	"crypto/x509"
	"fmt"
)

func Hello() string {
	roots := x509.NewCertPool()
	ok := roots.AppendCertsFromPEM([]byte(""))
	return fmt.Sprintf("Result: %v", ok)
}

Then run the command: gomobile build -target=ios .

What did you expect to see?

It should compile withour error.

What did you see instead?

Error: "clang: error: invalid argument '-mmacosx-version-min=10.6' not allowed with '-mios-simulator-version-min=6.1'"

[ianlancetaylor]

CC @eliasnaur

[gopherbot]

Change https://golang.org/cl/119555 mentions this issue: cmd/gomobile: fix gomobile build of non-main packages for iOS