tools: implement v wipe-cache to ease cleaning up the cache on windows

cmd/tools/vwipe-cache.v

@@ -0,0 +1,13 @@
+module main
+
+import os
+import v.vcache
+
+fn main() {
+	mut cm := vcache.new_cache_manager([])
+	cpath := cm.basepath
+	if os.exists(cpath) && os.is_dir(cpath) {
+		os.rmdir_all(cpath)
+	}
+	println('V cache folder $cpath was wiped.')
+}

cmd/v/v.v

@@ -30,6 +30,7 @@ const (
 		'build-examples',
 		'build-vbinaries',
 		'setup-freetype',
+		'wipe-cache',
 		'doc',
 		'doctor',
 	]