unify vexe_path

vlib/compiler/cc.v

@@ -30,7 +30,7 @@ fn (v mut V) cc() {
 		return
 	}
 	v.build_thirdparty_obj_files()
-	vexe := vexe_path()
+	vexe := pref.vexe_path()
 	vdir := filepath.dir(vexe)
 	// Just create a C/JavaScript file and exit
 	// for example: `v -o v.c compiler`

vlib/compiler/main.v

@@ -733,7 +733,7 @@ pub fn (v &V) get_user_files() []string {
 	mut user_files := []string
 
     // See cmd/tools/preludes/README.md for more info about what preludes are
-	vroot := filepath.dir(vexe_path())
+	vroot := filepath.dir(pref.vexe_path())
 	preludes_path := filepath.join(vroot,'cmd','tools','preludes')
 	if v.pref.is_live {
 		user_files << filepath.join(preludes_path,'live_main.v')
@@ -844,16 +844,6 @@ pub fn (v &V) log(s string) {
 	println(s)
 }
 
-pub fn vexe_path() string {
-	vexe := os.getenv('VEXE')
-	if '' != vexe {
-		return vexe
-	}
-	real_vexe_path := os.realpath(os.executable())
-	os.setenv('VEXE', real_vexe_path, true)
-	return real_vexe_path
-}
-
 pub fn verror(s string) {
 	println('V error: $s')
 	os.flush_stdout()

vlib/compiler/module_header.v

@@ -28,7 +28,7 @@ mut:
 // `mod` == "vlib/os"
 fn generate_vh(mod string) {
 	println('\n\n\n\nGenerating a V header file for module `$mod`')
-	vexe := vexe_path()
+	vexe := pref.vexe_path()
 	full_mod_path := filepath.join(filepath.dir(vexe),mod)
 	dir := if mod.starts_with('vlib') { '$compiler.v_modules_path${filepath.separator}$mod' } else { mod }
 	path := dir + '.vh'