compiler: support ctags with -print_v_files and .ctags.d/v.ctags

vlib/v/builder/builder.v

@@ -82,6 +82,13 @@ pub fn (mut b Builder) parse_imports() {
 		}
 	}
 	b.resolve_deps()
+	//
+	if b.pref.print_v_files {
+		for p in b.parsed_files {
+			println(p.path)
+		}
+		exit(0)        
+	}
 }
 
 pub fn (mut b Builder) resolve_deps() {

vlib/v/builder/c.v

@@ -33,10 +33,11 @@ pub fn (mut b Builder) gen_c(v_files []string) string {
 pub fn (mut b Builder) build_c(v_files []string, out_file string) {
 	b.out_name_c = out_file
 	b.info('build_c($out_file)')
+	output := b.gen_c(v_files)
 	mut f := os.create(out_file) or {
 		panic(err)
 	}
-	f.writeln(b.gen_c(v_files))
+	f.writeln(output)
 	f.close()
 	// os.write_file(out_file, b.gen_c(v_files))
 }

vlib/v/builder/js.v

@@ -29,10 +29,11 @@ pub fn (mut b Builder) gen_js(v_files []string) string {
 pub fn (mut b Builder) build_js(v_files []string, out_file string) {
 	b.out_name_js = out_file
 	b.info('build_js($out_file)')
+	output := b.gen_js(v_files)
 	mut f := os.create(out_file) or {
 		panic(err)
 	}
-	f.writeln(b.gen_js(v_files))
+	f.writeln(output)
 	f.close()
 }
 

vlib/v/pref/pref.v

@@ -80,6 +80,7 @@ pub mut:
 	mod                 string
 	run_args            []string // `v run x.v 1 2 3` => `1 2 3`
 	printfn_list        []string // a list of generated function names, whose source should be shown, for debugging
+	print_v_files       bool     // when true, just print the list of all parsed .v files then stop. 
 }
 
 pub fn backend_from_string(s string) ?Backend {