tests: add vlib/v/tests/skip_unused/

vlib/v/compiler_errors_test.v

@@ -57,6 +57,7 @@ fn test_all() {
 	module_dir := '$checker_dir/modules'
 	global_dir := '$checker_dir/globals'
 	run_dir := '$checker_dir/run'
+	skip_unused_dir := 'vlib/v/tests/skip_unused'
 	//
 	checker_tests := get_tests_in_dir(checker_dir, false)
 	parser_tests := get_tests_in_dir(parser_dir, false)
@@ -64,6 +65,7 @@ fn test_all() {
 	global_tests := get_tests_in_dir(global_dir, false)
 	module_tests := get_tests_in_dir(module_dir, true)
 	run_tests := get_tests_in_dir(run_dir, false)
+	skip_unused_dir_tests := get_tests_in_dir(skip_unused_dir, false)
 	// -prod is used for the parser and checker tests, so that warns are errors
 	mut tasks := Tasks{
 		vexe: vexe
@@ -83,6 +85,9 @@ fn test_all() {
 	tasks.add('', global_dir, '--enable-globals', '.out', global_tests, false)
 	tasks.add('', module_dir, '-prod run', '.out', module_tests, true)
 	tasks.add('', run_dir, 'run', '.run.out', run_tests, false)
+	tasks.add('', skip_unused_dir, 'run', '.run.out', skip_unused_dir_tests, false)
+	tasks.add('', skip_unused_dir, '-skip-unused run', '.skip_unused.run.out', skip_unused_dir_tests,
+		false)
 	tasks.run()
 	if github_job == 'ubuntu-tcc' {
 		// these should be run serially, since they depend on setting and using environment variables

vlib/v/tests/skip_unused/hw.run.out

@@ -0,0 +1 @@
+Hello, World!

vlib/v/tests/skip_unused/hw.skip_unused.run.out

@@ -0,0 +1 @@
+Hello, World!

vlib/v/tests/skip_unused/hw.vv

@@ -0,0 +1 @@
+println('Hello, World!')

vlib/v/tests/skip_unused/println_os_executable.run.out

@@ -0,0 +1 @@
+println_os_executable

vlib/v/tests/skip_unused/println_os_executable.skip_unused.run.out

@@ -0,0 +1 @@
+println_os_executable

vlib/v/tests/skip_unused/println_os_executable.vv

@@ -0,0 +1,7 @@
+import os
+
+fn main() {
+	x := os.args[0]
+	last_segment := x.replace('\\', '/').all_after('vlib/v/tests/skip_unused/')
+	println(last_segment)
+}