Compiling: Add instructions for macOS templates

Fixes #3194.

(cherry picked from commit f2ad006c373f70efca4e87d0bb3e99bbb7d80346)

development/compiling/compiling_for_osx.rst

@@ -82,6 +82,51 @@ use::
 
     scons platform=server tools=no target=release --jobs=$(sysctl -n hw.logicalcpu)
 
+Building export templates
+-------------------------
+
+To build macOS export templates, you have to compile with ``tools=no`` (no
+editor) and respectively for ``target=release`` (release template) and
+``target=release_debug``.
+
+Official templates are universal binaries which support both Intel x86_64 and
+ARM64 architectures. You can also create export templates that support only one
+of those two architectures by leaving out the ``lipo`` step below.
+
+- For Intel x86_64::
+
+    scons platform=osx tools=no target=release arch=x86_64 --jobs=$(sysctl -n hw.logicalcpu)
+    scons platform=osx tools=no target=release_debug arch=x86_64 --jobs=$(sysctl -n hw.logicalcpu)
+
+- For ARM64 (Apple M1)::
+
+    scons platform=osx tools=no target=release arch=arm64 --jobs=$(sysctl -n hw.logicalcpu)
+    scons platform=osx tools=no target=release_debug arch=arm64 --jobs=$(sysctl -n hw.logicalcpu)
+
+To support both architectures in a single "Universal 2" binary, run the above
+two commands blocks and then use ``lipo`` to bundle them together::
+
+    lipo -create bin/godot.osx.opt.x86_64 bin/godot.osx.opt.arm64 -output bin/godot.osx.opt.universal
+    lipo -create bin/godot.osx.opt.debug.x86_64 bin/godot.osx.opt.debug.arm64 -output bin/godot.osx.opt.debug.universal
+
+To create an ``.app`` bundle like in the official builds, you need to use the
+template located in ``misc/dist/osx_template.app``. The release and debug
+builds should be placed in ``osx_template.app/Contents/MacOS`` with the names
+``godot_osx_release.64`` and ``godot_osx_debug.64`` respectively. You can do so
+with the following commands (assuming a universal build, otherwise replace the
+``.universal`` extension with the one of your arch-specific binaries)::
+
+    cp -r misc/dist/osx_template.app .
+    mkdir -p osx_template.app/Contents/MacOS
+    cp bin/godot.osx.opt.universal osx_template.app/Contents/MacOS/godot_osx_release.64
+    cp bin/godot.osx.opt.debug.universal osx_template.app/Contents/MacOS/godot_osx_debug.64
+    chmod +x Godot.app/Contents/MacOS/godot_osx*
+
+You can then zip the ``osx_template.app`` folder to reproduce the ``osx.zip``
+template from the official Godot distribution::
+
+    zip -q -9 -r osx.zip osx_template.app
+
 Cross-compiling for macOS from Linux
 ------------------------------------