internal/buildcfg: enable regabi for Android
internal/buildcfg: enable regabi for Android

This will permit us to write ABIInternal assembler code for linux-amd64.

For #40724

Change-Id: I681866651554eda4229d6faa7f0c1ba42d07e57d
Reviewed-on: https://go-review.googlesource.com/c/go/+/315390
Trust: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
Run-TryBot: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
TryBot-Result: Go Bot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Cherry Zhang <d62e63aa42ce272d7b6a5055d97e942b33a34679@google.com>

CAFxX/go,golang/go,cloudflare/go,nawawi/go,cloudflare/go,CAFxX/go,CAFxX/go,CAFxX/go,cloudflare/go,golang/go,cloudflare/go,golang/go,cloudflare/go,nawawi/go,golang/go,cloudflare/go,CAFxX/go,golang/go,nawawi/go,golang/go,nawawi/go,nawawi/go,golang/go,nawawi/go,nawawi/go,golang/go,cloudflare/go,CAFxX/go,CAFxX/go,cloudflare/go,CAFxX/go,nawawi/go