builtin: make panics more IDE friendly

cmd/tools/vtest-self.v

@@ -207,7 +207,7 @@ fn main() {
 	args := os.args.clone()
 	args_string := args[1..].join(' ')
 	cmd_prefix := args_string.all_before('test-self')
-	title := 'testing all tests'
+	title := 'testing vlib'
 	all_test_files := os.walk_ext(os.join_path(vroot, 'vlib'), '_test.v')
 	testing.eheader(title)
 	mut tsession := testing.new_test_session(cmd_prefix)

vlib/builtin/builtin.c.v

@@ -22,8 +22,7 @@ fn panic_debug(line_no int, file string, mod string, fn_name string, s string) {
 	eprintln('   module: $mod')
 	eprintln(' function: ${fn_name}()')
 	eprintln('  message: $s')
-	eprintln('     file: $file')
-	eprintln('     line: ' + line_no.str())
+	eprintln('     file: $file:$line_no')
 	eprintln('=========================================')
 	$if exit_after_panic_message ? {
 		C.exit(1)

vlib/v/builder/cc.v

@@ -138,7 +138,7 @@ fn (mut v Builder) rebuild_cached_module(vexe string, imp_path string) string {
 		vcache.dlog('| Builder.' + @FN, 'vexe: $vexe | imp_path: $imp_path | rebuild_cmd: $rebuild_cmd')
 		os.system(rebuild_cmd)
 		rebuilded_o := v.pref.cache_manager.exists('.o', imp_path) or {
-			panic('could not rebuild cache module for $imp_path, error: $err')
+			panic('could not rebuild cache module for $imp_path, error: $err.msg')
 		}
 		os.chdir(pwd)
 		return rebuilded_o

vlib/v/tests/inout/panic_with_cg.out

@@ -2,5 +2,4 @@
    module: main
  function: buggy_function()
   message: panicing...
-     file: vlib/v/tests/inout/panic_with_cg.vv
-     line: 3
+     file: vlib/v/tests/inout/panic_with_cg.vv:3