builder: print collected checker warnings too

vlib/v/builder/builder.v

@@ -275,6 +275,15 @@ fn (b &Builder) print_errors(errors []errors.Error) {
 	}
 }
 
+fn (b &Builder) print_warnings(warnings []errors.Warning) {
+	for err in warnings {
+		kind := if b.pref.is_verbose { '$err.reporter warning #$b.checker.nr_errors:' } else { 'warning:' }
+		ferror := util.formatted_error(kind, err.message, err.file_path, err.pos)
+		eprintln(ferror)
+	}
+}
+
+
 fn verror(s string) {
 	util.verror('builder error', s)
 }

vlib/v/builder/c.v

@@ -18,6 +18,9 @@ pub fn (mut b Builder) gen_c(v_files []string) string {
 	t2 := time.ticks()
 	check_time := t2 - t1
 	b.info('CHECK: ${check_time}ms')
+	if b.checker.nr_warnings > 0 {
+		b.print_warnings(b.checker.warnings)
+	}
 	if b.checker.nr_errors > 0 {
 		b.print_errors(b.checker.errors)
 		exit(1)

vlib/v/checker/checker.v

@@ -21,6 +21,7 @@ pub struct Checker {
 mut:
 	file           ast.File
 	nr_errors      int
+	nr_warnings    int
 	errors         []errors.Error
 	warnings       []errors.Warning
 	error_lines    []int // to avoid printing multiple errors for the same line
@@ -1969,6 +1970,7 @@ fn (mut c Checker) warn_or_error(message string, pos token.Position, warn bool)
 	// print_backtrace()
 	// }
 	if warn {
+		c.nr_warnings++
 		c.warnings << errors.Warning{
 			reporter: errors.Reporter.checker
 			pos: pos