cleanup simplification for diagnosing failure

Author: spytheman

vlib/v/pref/vsh_envbang_test.v

@@ -21,8 +21,7 @@ println('hello')
 println(os.args)
 ")!
 	os.chmod(rnd_vsh_script_path, 0o700)!
-	cmd := '${os.quoted_path(rnd_vsh_script_path)} abc 123 -option'
-	res := os.execute(cmd)
+	res := os.execute('${os.quoted_path(rnd_vsh_script_path)} abc 123 -option')
 	assert res.exit_code == 0
 	lines := res.output.split_into_lines()
 	assert lines[0] == 'hello'