[feature request] Implement promise resolver for 'mesonbuild.build'.

[RolfNoot]

Hi,

In an external extension I'm calling await vscode.commands.executeCommand("mesonbuild.build", ""); Unfortunately the function returns immediately without awaiting the build results. I need to wait on completion of the build as this command is part of the prelauch task.

I changed runMesonBuild to solve this issue (I'm not an experienced JS programmer but this works):

export async function runMesonBuild(buildDir: string, name?: string) {
    try {
        let buildTask = await getTask(vscode, "build", name);
        const buildTaskExecution = await vscode.tasks.executeTask(buildTask);
        return new Promise((resolve) => {
            vscode.tasks.onDidEndTaskProcess(e => {
                if (e.execution === buildTaskExecution || e.execution.task === buildTask) 
                    resolve(e.exitCode);
            });
        });
    } catch (e) {
    vscode.window.showErrorMessage(`Could not build ${name}`);
    getOutputChannel().appendLine(`Building target ${name}:`);
    getOutputChannel().appendLine(e);
    getOutputChannel().show(true);
    return new Promise((resolve, reject) => reject(e));
    }
  }

Any chance to have this implemented?
Regards, Rolf