no 'g' either for browser compatibility

Author: ieviev

src/fable-library-ts/RegExp.ts

@@ -12,10 +12,11 @@ export function create(pattern: string, options = 0) {
     throw new Error("RegexOptions only supports: IgnoreCase, Multiline, Compiled, Singleline, ECMAScript and NonBacktracking");
   }
 
+  let flags = "";
   // Set global and unicode flags for compatibility with dotnet, see #2925
-  let flags = "g";
-  // add unicode only if not NonBacktracking, 'l' and 'u' together are not allowed
-  flags += options & 1024 ? "l" : "u";
+  // for NonBacktracking, add just 'l', ('u' + 'l' is unsupported, 'g' + 'l'
+  // is supported only with '--enable-experimental-regexp-engine')
+  flags += options & 1024 ? "l" : "gu";
   flags += options & 1 ? "i" : ""; // 0x0001 RegexOptions.IgnoreCase
   flags += options & 2 ? "m" : "";
   flags += options & 16 ? "s" : "";