gradle command results in 'program not found' error on Windows

[heilhead]

On Windows, gradle fails to be invoked as a Command here (failing with the 'program not found' error):

xbuild/xbuild/src/gradle/mod.rs

Line 160 in 268939a

let mut cmd = Command::new("gradle");

The gradle.bat is a batch file and needs to be executed via cmd:

    let mut cmd = if cfg!(target_os = "windows") {
        let mut cmd = Command::new("cmd");
        cmd.args(["/c", "gradle"]);
        cmd
    } else {
        Command::new("gradle")
    };

Also, the doctor command successfully resolves gradle to gradle.bat using which crate, but then Command fails to execute it. A bit misleading and needs to be addressed.