builder: support v.mod/@VROOT, fix -cflags and -cache

cmd/v/v.v

@@ -132,6 +132,7 @@ fn parse_args(args []string) (&pref.Preferences, string) {
 			'-obfuscate' {	res.obfuscate = true	}
 			'-translated' {	res.translated = true	}
 			'-showcc' {	res.show_cc = true	}
+			'-cache' {	res.is_cache = true	}
 			'-keepc' {	res.is_keep_c = true	}
 			//'-x64' {	res.translated = true	}
 			'-os' {
@@ -144,6 +145,10 @@ fn parse_args(args []string) (&pref.Preferences, string) {
 				res.os = tmp
 				i++
 			}
+			'-cflags' {
+				res.cflags = cmdline.option(args, '-cflags', '')
+				i++
+			}
 			'-cc' {
 				res.ccompiler = cmdline.option(args, '-cc', 'cc')
 				i++

vlib/v/builder/builder.v

@@ -7,6 +7,7 @@ import (
 	v.table
 	v.pref
 	v.util
+	v.vmod
 	v.checker
 	v.parser
 	v.gen
@@ -109,7 +110,7 @@ pub fn (b mut Builder) parse_imports() {
 			if mod in done_imports {
 				continue
 			}
-			import_path := b.find_module_path(mod) or {
+			import_path := b.find_module_path(mod, ast_file.path) or {
 				// v.parsers[i].error_with_token_index('cannot import module "$mod" (not found)', v.parsers[i].import_table.get_import_tok_idx(mod))
 				// break
 				// println('module_search_paths:')
@@ -267,9 +268,16 @@ fn module_path(mod string) string {
 	return mod.replace('.', os.path_separator)
 }
 
-pub fn (b Builder) find_module_path(mod string) ?string {
+pub fn (b Builder) find_module_path(mod string, fpath string) ?string {
+	// support @VROOT/v.mod relative paths:
+	vmod_file_location := vmod.mod_file_cacher.get( fpath )
 	mod_path := module_path(mod)
-	for search_path in b.module_search_paths {
+	mut module_lookup_paths := []string
+	if vmod_file_location.vmod_file.len != 0 && !(vmod_file_location.vmod_folder in b.module_search_paths) {
+		module_lookup_paths << vmod_file_location.vmod_folder
+	}
+	module_lookup_paths << b.module_search_paths
+	for search_path in module_lookup_paths {
 		try_path := os.join_path(search_path, mod_path)
 		if b.pref.is_verbose {
 			println('  >> trying to find $mod in $try_path ..')
@@ -281,7 +289,8 @@ pub fn (b Builder) find_module_path(mod string) ?string {
 			return try_path
 		}
 	}
-	return error('module "$mod" not found')
+	smodule_lookup_paths := module_lookup_paths.join(', ')
+	return error('module "$mod" not found in:\n$smodule_lookup_paths')
 }
 
 fn verror(s string) {

vlib/v/builder/cc.v

@@ -169,7 +169,13 @@ fn (v mut Builder) cc() {
 			}
 		}
 	}
-	if v.pref.ccompiler.contains('clang') || guessed_compiler == 'clang' {
+	//
+	is_cc_clang := v.pref.ccompiler.contains('clang') || guessed_compiler == 'clang'
+	is_cc_tcc  := v.pref.ccompiler.contains('tcc') || guessed_compiler == 'tcc'
+	is_cc_gcc  := v.pref.ccompiler.contains('gcc') || guessed_compiler == 'gcc'
+	is_cc_msvc := v.pref.ccompiler.contains('msvc') || guessed_compiler == 'msvc'
+	//
+	if is_cc_clang {
 		if debug_mode {
 			debug_options = '-g -O0 -no-pie'
 		}
@@ -182,7 +188,7 @@ fn (v mut Builder) cc() {
 			optimization_options += ' -flto'
 		}
 	}
-	if v.pref.ccompiler.contains('gcc') || guessed_compiler == 'gcc' {
+	if is_cc_gcc {
 		if debug_mode {
 			debug_options = '-g3 -no-pie'
 		}
@@ -302,8 +308,17 @@ fn (v mut Builder) cc() {
 	a << cflags.c_options_without_object_files()
 	a << libs
 
-	if v.pref.show_cc {
-		a << pref.default_module_path + '/cache/vlib/builtin.o'
+	if v.pref.is_cache {
+		cached_files := ['builtin.o', 'math.o']
+		for cfile in cached_files {
+			ofile := os.join_path(pref.default_module_path, 'cache', 'vlib', cfile)
+			if os.exists(ofile) {
+				a << ofile
+			}
+		}
+		if !is_cc_tcc {
+			a << '-Xlinker -z -Xlinker muldefs'
+		}
 	}
 
 	// Without these libs compilation will fail on Linux

vlib/v/builder/compile.v

@@ -139,7 +139,7 @@ fn (v mut Builder) set_module_lookup_paths() {
 	v.module_search_paths << os.join_path(v.compiled_dir, 'modules')
 	v.module_search_paths << v.pref.lookup_path
 	if v.pref.is_verbose {
-		v.log('v.module_lookup_paths')		// : $v.module_lookup_paths')
+		v.log('v.module_search_paths:')
 		println(v.module_search_paths)
 	}
 }

vlib/v/gen/cgen.v

@@ -848,7 +848,7 @@ fn (g mut Gen) gen_fn_decl(it ast.FnDecl) {
 */
 	//
 	g.fn_args(it.args, it.is_variadic)
-	if it.no_body || (g.pref.show_cc && it.is_builtin) {
+	if it.no_body || (g.pref.is_cache && it.is_builtin) {
 		// Just a function header.
 		// Builtin function bodies are defined in builtin.o
 		g.definitions.writeln(');')