[gjs/fix-windows] arg-cache.cpp: Overload bitwise OR for GjsArgumentFlags

[Chun-wei Fan <fanchunwei src gnome org>]

commit 2404cafb26d696ce4d4d0e7249f5211384fd34ec
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Wed Jan 12 13:47:17 2022 +0800

    arg-cache.cpp: Overload bitwise OR for GjsArgumentFlags
    
    This way, we avoid getting C2440 errors on Visual Studio, where it is quite
    particular about the type conversions that we can perform by default.

 gi/arg-cache.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)
---
diff --git a/gi/arg-cache.cpp b/gi/arg-cache.cpp
index 603f1502..94f0d129 100644
--- a/gi/arg-cache.cpp
+++ b/gi/arg-cache.cpp
@@ -189,6 +189,14 @@ struct Nullable {
     }
 };
 
+// Overload operator| so that Visual Studio won't complain
+// when converting unsigned char to GjsArgumentFlags
+GjsArgumentFlags operator|(
+    GjsArgumentFlags const& v1, GjsArgumentFlags const& v2) {
+    return static_cast<GjsArgumentFlags>(std::underlying_type<GjsArgumentFlags>::type(v1) |
+                                         std::underlying_type<GjsArgumentFlags>::type(v2));
+}
+
 struct Positioned {
     void set_arg_pos(int pos) {
         g_assert(pos <= Argument::MAX_ARGS &&