Windows binaries don't run on Windows 7

Describe the bug:

Binaries built on macOS run on Windows 10 Pro, but not on Windows 7 Home Edition Premium.

To Reproduce:

Steps to reproduce the behaviour:

1. On macOS, copy the First App from https://developer.fyne.io/started/firstapp, procure an image to use as an icon, say someimage.png
2. Install the XCode CLI development tools with xcode-select --install
3. Install MinGW with brew install mingw-w64
4. Build the app with CGO_ENABLED=1 CC=x86_64-w64-mingw32-gcc fyne package -os windows -icon someimage.png
5. Check the binary with file firstapp.exe, it shows PE32+ executable (GUI) x86-64, for MS Windows.
6. Transfer the binary to a W10 PRo and a W7 machine.
7. It runs on the former, and is rejected on the latter, with an error about it not being for the proper windows version.
8. Alternatively, trying to build a 32-bit version with CGO_ENABLED=1 CC=i686-w64-mingw32-gcc fyne package -os windows -icon someimage.png fails with cc1: sorry, unimplemented: 64-bit mode not compiled in.

Device (please complete the following information):

• OS: Dev: macOS, Target: Windows
• Version: Dev: both Catalina and Big Sur, Target: Windows 10 Pro, Windows 7 Home Edition Premium
• Go version: 1.15.8
• Fyne version: fyne.io/fyne/v2 v2.0.0