cmd/fyne: support -os iossimulator

[changkun]

Description:

This PR adds -os iossimulator to the fyne command, and fixes the iOS simulator issue on darwin/arm64.

Fixes #1917

Checklist:

• Tests included.
• Lint and formatter run with no errors.
• Tests all pass.

[andydotxyz]

Do we need another target system to support this? the iOS package already includes both amd64 and arm64...
Unfortunately on my system iOS builds with or without this patch do not run on the simulator and I have not been able to figure out why.

[changkun]

Do we need another target system to support this? the iOS package already includes both amd64 and arm64...

Yes, but only works for darwin/amd64 systems. The iOS simulator fails on M1 macs.
Packing darwin/arm64 for device and darwin/arm64 for iOS seems impossible when using xcrun lipo. As they have the same architecture. Adding a iossimulator better isolates ios targets and iossimulator targets.

[andydotxyz]

There must be a way to support this new feature without removing 32bit iOS support?

[changkun]

My darwin/amd64 was broken recently and have been sent to a repair center which might take weeks to repair.

After rebase based on the latest develop branch, I could not even run fyne package -os iossimulator on darwin/arm64, and got: go: unsupported GOOS/GOARCH pair iossimulator/arm64

Looks like I have completely lost track here.

[changkun]

I think I've figured the problem. As I tested the latest status of this PR on two of my Macs, it has fixed the previous concerned issue. Now the code works both for ios/arm, ios/arm64, ios/amd64, iossimulator/amd64, iossimulator/arm64 on either amd64 Macs or arm64 Macs.

PTAL.

[andydotxyz]

Tested and working well thanks.
It is a shame about the duplicate file, but I guess with the import issues it is not possible to resolve another way?
We can remove the old file once we stop supporting Go 1.14 ;)