v.pref: fix ./v -usecache -cg run examples/hello_world.v

cmd/tools/vtest-all.v

@@ -129,6 +129,11 @@ fn get_all_commands() []Command {
 		line: '$vexe install nedpals.args'
 		okmsg: '`v install` works.'
 	}
+	res << Command{
+		line: '$vexe -usecache -cg examples/hello_world.v'
+		okmsg: '`v -usecache -cg` works.'
+		rmfile: 'examples/hello_world'
+	}
 	// NB: test that a program that depends on thirdparty libraries with its
 	// own #flags (tetris depends on gg, which uses sokol) can be compiled
 	// with -usecache:

vlib/v/pref/default.v

@@ -116,9 +116,9 @@ pub fn (mut p Preferences) fill_with_defaults() {
 		'$p.backend | $p.os | $p.ccompiler | $p.is_prod | $p.sanitize',
 		p.cflags.trim_space(),
 		p.third_party_option.trim_space(),
-		'$p.compile_defines_all',
-		'$p.compile_defines',
-		'$p.lookup_path',
+		p.compile_defines_all.str(),
+		p.compile_defines.str(),
+		p.lookup_path.str(),
 	])
 	// eprintln('prefs.cache_manager: $p')
 	// disable use_cache for specific cases:

vlib/v/pref/pref.v

@@ -806,7 +806,9 @@ pub fn get_host_arch() Arch {
 
 fn parse_define(mut prefs Preferences, define string) {
 	define_parts := define.split('=')
-	prefs.build_options << '-d $define'
+	if !(prefs.is_debug && define == 'debug') {
+		prefs.build_options << '-d $define'
+	}
 	if define_parts.len == 1 {
 		prefs.compile_defines << define
 		prefs.compile_defines_all << define