Add support for passing custom build tags

[Stoyvo]

Describe the bug:

Fyne offers a package command, however package is also building. In my case, I need to compile my binary with TAGLIB, I use the following:
go build --tags "darwin libtag" -v

Fyne package should be responsible for the certificate, versioning, packaging, and the building should be optional, or provide a way to allow additional tags to be configured.

[andydotxyz]

You can do this by telling the fyne tool that the binary already exists with the -executable parameter.
If that file is found it should not trigger a build.

[Stoyvo]

@andydotxyz Yes, but the fyne tool has its own parameters for windows builds, Eg:
https://github.com/fyne-io/fyne/blob/master/cmd/fyne/commands/build.go#L24

	if goos == "windows" {
		if b.release {
			cmd = exec.Command("go", "build", "-ldflags", "-s -w -H=windowsgui", ".")
		} else {
			cmd = exec.Command("go", "build", "-ldflags", "-H=windowsgui", ".")
		}
	} else {
		if b.release {
			cmd = exec.Command("go", "build", "-ldflags", "-s -w", ".")
		} else {
			cmd = exec.Command("go", "build", ".")
		}
	}

If we provide that path, these flags aren't set unless we specify them specifically?

[andydotxyz]

Yes that is correct. Currently you either build manually, or you get fyne to handle it for you.

[andydotxyz]

Perhaps this ticket changes from a bug "Unable to package with custom build tags" to a feature request "Add support for passing custom build tags"?

[andydotxyz]

This could be related to fyne-io/fyne-cross#5

[Stoyvo]

Perhaps this ticket changes from a bug "Unable to package with custom build tags" to a feature request "Add support for passing custom build tags"?

@andydotxyz I agree with this, or we can track this as a documentation enhancement to better define what parameters are required for each OS.