enable building mono files without tools

Index: modules/mono/build_scripts/api_solution_build.py
--- modules/mono/build_scripts/api_solution_build.py.orig
+++ modules/mono/build_scripts/api_solution_build.py
@@ -47,7 +47,7 @@ def build_api_solution(source, target, env):
 
 
 def build(env_mono):
-    assert env_mono["tools"]
+    #assert env_mono["tools"]
 
     target_filenames = [
         "GodotSharp.dll",
