Mono/C#: Add iOS support

Right now, games only work on devices when exported with FullAOT+Interpreter.
There are some issues left that need to addressed for FullAOT alone. Right now,
it's giving issues with the Godot.NativeCalls static constructor.

modules/mono/build_scripts/mono_configure.py

@@ -48,16 +48,19 @@ def find_file_in_dir(directory, names, prefixes=[""], extensions=[""]):
     return ""
 
 
-def copy_file(src_dir, dst_dir, name):
+def copy_file(src_dir, dst_dir, src_name, dst_name=""):
     from shutil import copy
 
-    src_path = os.path.join(Dir(src_dir).abspath, name)
+    src_path = os.path.join(Dir(src_dir).abspath, src_name)
     dst_dir = Dir(dst_dir).abspath
 
     if not os.path.isdir(dst_dir):
         os.makedirs(dst_dir)
 
-    copy(src_path, dst_dir)
+    if dst_name:
+        copy(src_path, os.path.join(dst_dir, dst_name))
+    else:
+        copy(src_path, dst_dir)
 
 
 def is_desktop(platform):
@@ -65,11 +68,11 @@ def is_desktop(platform):
 
 
 def is_unix_like(platform):
-    return platform in ["osx", "linuxbsd", "server", "android", "haiku"]
+    return platform in ["osx", "linuxbsd", "server", "android", "haiku", "iphone"]
 
 
 def module_supports_tools_on(platform):
-    return platform not in ["android", "javascript"]
+    return platform not in ["android", "javascript", "iphone"]
 
 
 def find_wasm_src_dir(mono_root):
@@ -87,6 +90,8 @@ def configure(env, env_mono):
     bits = env["bits"]
     is_android = env["platform"] == "android"
     is_javascript = env["platform"] == "javascript"
+    is_ios = env["platform"] == "iphone"
+    is_ios_sim = is_ios and env["arch"] in ["x86", "x86_64"]
 
     tools_enabled = env["tools"]
     mono_static = env["mono_static"]
@@ -111,17 +116,32 @@ def configure(env, env_mono):
         raise RuntimeError("This module does not currently support building for this platform with tools enabled")
 
     if is_android and mono_static:
-        # Android: When static linking and doing something that requires libmono-native, we get a dlopen error as libmono-native seems to depend on libmonosgen-2.0
-        raise RuntimeError("Statically linking Mono is not currently supported on this platform")
+        # FIXME: When static linking and doing something that requires libmono-native, we get a dlopen error as 'libmono-native'
+        # seems to depend on 'libmonosgen-2.0'. Could be fixed by re-directing to '__Internal' with a dllmap or in the dlopen hook.
+        raise RuntimeError("Statically linking Mono is not currently supported for this platform")
 
-    if is_javascript:
-        mono_static = True
+    if not mono_static and (is_javascript or is_ios):
+        raise RuntimeError("Dynamically linking Mono is not currently supported for this platform")
 
     if not mono_prefix and (os.getenv("MONO32_PREFIX") or os.getenv("MONO64_PREFIX")):
         print(
             "WARNING: The environment variables 'MONO32_PREFIX' and 'MONO64_PREFIX' are deprecated; use the 'mono_prefix' SCons parameter instead"
         )
 
+    # Although we don't support building with tools for any platform where we currently use static AOT,
+    # if these are supported in the future, we won't be using static AOT for them as that would be
+    # too restrictive for the editor. These builds would probably be made to only use the interpreter.
+    mono_aot_static = (is_ios and not is_ios_sim) and not env["tools"]
+
+    # Static AOT is only supported on the root domain
+    mono_single_appdomain = mono_aot_static
+
+    if mono_single_appdomain:
+        env_mono.Append(CPPDEFINES=["GD_MONO_SINGLE_APPDOMAIN"])
+
+    if (env["tools"] or env["target"] != "release") and not mono_single_appdomain:
+        env_mono.Append(CPPDEFINES=["GD_MONO_HOT_RELOAD"])
+
     if env["platform"] == "windows":
         mono_root = mono_prefix
 
@@ -193,6 +213,7 @@ def configure(env, env_mono):
             copy_file(mono_bin_path, "#bin", mono_dll_file)
     else:
         is_apple = env["platform"] in ["osx", "iphone"]
+        is_macos = is_apple and not is_ios
 
         sharedlib_ext = ".dylib" if is_apple else ".so"
 
@@ -200,12 +221,12 @@ def configure(env, env_mono):
         mono_lib_path = ""
         mono_so_file = ""
 
-        if not mono_root and (is_android or is_javascript):
+        if not mono_root and (is_android or is_javascript or is_ios):
             raise RuntimeError(
                 "Mono installation directory not found; specify one manually with the 'mono_prefix' SCons parameter"
             )
 
-        if not mono_root and is_apple:
+        if not mono_root and is_macos:
             # Try with some known directories under OSX
             hint_dirs = ["/Library/Frameworks/Mono.framework/Versions/Current", "/usr/local/var/homebrew/linked/mono"]
             for hint_dir in hint_dirs:
@@ -223,6 +244,9 @@ def configure(env, env_mono):
                     + "specify one manually with the 'mono_prefix' SCons parameter"
                 )
 
+        if is_ios and not is_ios_sim:
+            env_mono.Append(CPPDEFINES=["IOS_DEVICE"])
+
         if mono_root:
             print("Found Mono root directory: " + mono_root)
 
@@ -244,7 +268,26 @@ def configure(env, env_mono):
                 mono_lib_file = os.path.join(mono_lib_path, "lib" + mono_lib + ".a")
 
                 if is_apple:
-                    env.Append(LINKFLAGS=["-Wl,-force_load," + mono_lib_file])
+                    if is_macos:
+                        env.Append(LINKFLAGS=["-Wl,-force_load," + mono_lib_file])
+                    else:
+                        arch = env["arch"]
+
+                        def copy_mono_lib(libname_wo_ext):
+                            copy_file(
+                                mono_lib_path, "#bin", libname_wo_ext + ".a", "%s.iphone.%s.a" % (libname_wo_ext, arch)
+                            )
+
+                        # Copy Mono libraries to the output folder. These are meant to be bundled with
+                        # the export templates and added to the Xcode project when exporting a game.
+                        copy_mono_lib("lib" + mono_lib)
+                        copy_mono_lib("libmono-native")
+                        copy_mono_lib("libmono-profiler-log")
+
+                        if not is_ios_sim:
+                            copy_mono_lib("libmono-ee-interp")
+                            copy_mono_lib("libmono-icall-table")
+                            copy_mono_lib("libmono-ilgen")
                 else:
                     assert is_desktop(env["platform"]) or is_android or is_javascript
                     env.Append(LINKFLAGS=["-Wl,-whole-archive", mono_lib_file, "-Wl,-no-whole-archive"])
@@ -281,10 +324,12 @@ def configure(env, env_mono):
             else:
                 env.Append(LIBS=[mono_lib])
 
-            if is_apple:
+            if is_macos:
                 env.Append(LIBS=["iconv", "pthread"])
             elif is_android:
                 pass  # Nothing
+            elif is_ios:
+                pass  # Nothing, linking is delegated to the exported Xcode project
             elif is_javascript:
                 env.Append(LIBS=["m", "rt", "dl", "pthread"])
             else:
@@ -344,6 +389,8 @@ def configure(env, env_mono):
             copy_mono_shared_libs(env, mono_root, None)
         elif is_javascript:
             pass  # No data directory for this platform
+        elif is_ios:
+            pass  # No data directory for this platform
 
     if copy_mono_root:
         if not mono_root: