Apply min macOS version as 10.11 like the app store packaging

[andydotxyz]

This suppports most computers sold in the last 12 years
and goes beyond Apple support plans.

Fixes #886

Can test with:
otool -l MyApp.app/Contents/MacOS/MyApp | grep -b4 VERSION_MIN_MACOSX

Checklist:

• Tests included. <- manual inspection of the output binary
• Lint and formatter run with no errors.
• Tests all pass.

[Jacalz]

This is a really nice change. Go 1.15 dropped support for 10.11, should we perhaps instead have 10.12 as the least supported?

[andydotxyz]

Thanks, but I'm not sure I agree - We still support Go 1.12 so we cannot only support target platforms of Go 1.15.
The 32bit support was a little different as we litereally could not build the apps any more - but for OS versioning we should be OK to support older.

[Jacalz]

Oh, I see. The removal of 32bit in 1.15 was why I asked. Did not know that we literally couldn’t build them. Left a little suggestion, otherwise I think it is fine 🙂