Meta: Add the base64 utility to the GN build

Meta/gn/secondary/BUILD.gn

@@ -6,6 +6,7 @@ group("default") {
     "//Meta/Lagom/Tools/CodeGenerators/IPCCompiler",
     "//Tests",
     "//Userland/Libraries/LibWeb",
+    "//Userland/Utilities:base64",
     "//Userland/Utilities:js",
   ]
   testonly = true

Meta/gn/secondary/Userland/Utilities/BUILD.gn

@@ -1,3 +1,13 @@
+executable("base64") {
+  sources = [ "base64.cpp" ]
+  include_dirs = [ "//Userland/Libraries" ]
+  deps = [
+    "//AK",
+    "//Userland/Libraries/LibCore",
+    "//Userland/Libraries/LibMain",
+  ]
+}
+
 executable("js") {
   sources = [ "js.cpp" ]
   include_dirs = [ "//Userland/Libraries" ]