x/mobile/cmd/gomobile: gomobile build on simple program returns "ld: error: duplicate symbol: x_cgo_inittls" [1.14 backport]

[gopherbot]

@ianlancetaylor requested issue #42655 to be considered for backport to the next 1.14 minor release.

@gopherbot Please open backport issues

Although this was filed against x/mobile, the fix is to runtime/cgo in the standard library. This is caused by a change in the default behavior of the C compiler. Anybody using an older release of Go with a new C compiler will run into this problem. Since the fix is small and safe, we should backport it.