[XM] Only use bgen, not bmac[-mobile-mono]. Fixes #3675. (#4785)

We don't need to use a custom mono to run the generator anymore, so stop doing
it.

Unfortunately we can't remove the custom mono, since we're now using it for
another purpose (AOT-compiling XM apps).

Fixes https://github.com/xamarin/xamarin-macios/issues/3675.

docs/website/binding_types_reference_guide.md

@@ -1340,8 +1340,8 @@ The following shows two such properties in Objective-C:
 When you apply the `DisposeAttribute` to a class, you provide a code snippet
 that will be added to the `Dispose()` method implementation of the class.
 
-Since the `Dispose` method is automatically generated by the `bmac-native` and `btouch-native`
-tools, you need to use the `Dispose` attribute to inject some code in the
+Since the `Dispose` method is automatically generated by the `bgen`
+tool, you need to use the `Dispose` attribute to inject some code in the
 generated `Dispose` method implementation.
 
 For example:

msbuild/Xamarin.Mac.Tasks/Xamarin.Mac.ObjCBinding.Common.props

@@ -27,8 +27,7 @@ Copyright (C) 2014 Xamarin. All rights reserved.
 	<PropertyGroup>
 		<BaseLibDllPath>$(MacBclPath)/Xamarin.Mac.dll</BaseLibDllPath>
 		<BTouchToolPath>$(XamarinMacFrameworkRoot)/bin/</BTouchToolPath>
-		<BTouchToolExe Condition="Exists('$(BTouchToolPath)/bgen')">bgen</BTouchToolExe>
-		<BTouchToolExe Condition="!Exists('$(BTouchToolPath)/bgen')">bmac-mobile-mono</BTouchToolExe>
+		<BTouchToolExe>bgen</BTouchToolExe>
 		<AllowUnsafeBlocks>True</AllowUnsafeBlocks>
 
 		<DefineConstants>__UNIFIED__;__MACOS__;$(DefineConstants)</DefineConstants>

src/bmac

@@ -43,7 +43,7 @@ sdk=$(echo $sdk | tr '[:upper:]' '[:lower:]')
 case $sdk in
 mobile|xamarin.mac|xammac)
 	bmac="bmac-mobile.exe -no-mono-path"
-	mono=$ROOT_DIR/bin/bmac-mobile-mono
+	mono=/Library/Frameworks/Mono.framework/Commands/mono
 	export MONO_PATH=$ROOT_DIR/lib/mono/Xamarin.Mac
 	;;
 *)
@@ -60,7 +60,6 @@ mobile|xamarin.mac|xammac)
 			refs="-baselib:$ROOT_DIR/lib/reference/mobile/Xamarin.Mac.dll --target-framework=Xamarin.Mac,Version=v2.0,Profile=Mobile"
 			bmac=bmac-mobile.exe
 			export MONO_PATH=$ROOT_DIR/lib/mono/Xamarin.Mac
-			mono="$ROOT_DIR/bin/bmac-mobile-mono"
 		fi
 	fi
 	;;