Throw a more descriptive exception when the binary was not created

When the build command fails and a binary was not created, this results in an error like `rename(app.phar, builds/app): the system cannot find the file specified `. This is not very descriptive to the actual issue, so this PR adds a check to thrown an exception if the file was not created. This will make debugging easier.

See laravel-zero/laravel-zero#461

src/Commands/BuildCommand.php

@@ -161,6 +161,10 @@ private function compile(string $name): BuildCommand
         $this->task('   2. <fg=yellow>Compile</> into a single file');
 
         $this->output->newLine();
+
+        if (! File::exists($this->app->basePath($this->getBinary()) . '.phar')) {
+            throw new \RuntimeException('Failed to compile the application.');
+        }
 
         File::move($this->app->basePath($this->getBinary()).'.phar', $this->app->buildsPath($name));