os template function doesn't match against BAKE_OS

[heybdj]

When the target OS is specified in the BAKE_OS environment variable, and when the target OS is different than the host OS, os template functions will fail to match against the target OS. For example:

In bake.json:

{
	"environment": {
		"ios": {
			"BAKE_OS": "ios",
			"BAKE_ARCHITECTURE": "arm64"
		}
	}
}

In project.json

"${os ios}": {
	"cflags":  [
		"-target $BAKE_ARCHITECTURE-apple-$BAKE_OS"
	]
}

The os check here fails to match because it compares against the host OS ("Darwin" in my case).

This could be intended behaviour, but, if so, I don't see any other mechanism in Bake for branching project settings off of the build target 😕

bake.load looks like it manages a similar set of OS-related strings as bake.util.os. And bake.load.ut_load_init(...) has this nice bit of code:

if (!os) {
    os = ut_getenv("BAKE_OS");
    if (!os) {
        os = UT_OS_STRING;
    }
}
// ...
UT_OS = ut_strdup(os);
// ...
ut_setenv("BAKE_OS", UT_OS);

UT_OS_STRING is always a representation of the host OS, and BAKE_OS is the same unless the user overrides it in their config. Given that, would it be safe and reasonable to change the OS-matching logic to compare against BAKE_OS instead of UT_OS_STRING?