Build SDL3 for ReadTheDocs workflow

Note PKG_CONFIG_PATH on pkg-config errors to debug issues with the
environment sent to Python setup scripts.

Author: HexDecimal

.readthedocs.yaml

@@ -9,7 +9,17 @@ build:
   tools:
     python: "3.11"
   apt_packages:
-    - libsdl3-dev
+    - build-essential
+    - make
+    - pkg-config
+    - cmake
+    - ninja-build
+  jobs:
+    pre_install:
+      - git clone --depth 1 --branch release-3.2.16 https://github.com/libsdl-org/SDL.git sdl_repo
+      - cmake -S sdl_repo -B sdl_build -D CMAKE_INSTALL_PREFIX=~/.local
+      - cmake --build sdl_build --config Debug
+      - cmake --install sdl_build
 
 submodules:
   include: all

setup.py

@@ -3,6 +3,7 @@
 
 from __future__ import annotations
 
+import os
 import platform
 import subprocess
 import sys
@@ -55,6 +56,10 @@ def check_sdl_version() -> None:
                 "\nsdl3-config must be on PATH."
             )
             raise RuntimeError(msg) from exc
+    except subprocess.CalledProcessError as exc:
+        if sys.version_info >= (3, 11):
+            exc.add_note(f"Note: {os.environ.get('PKG_CONFIG_PATH')=}")
+        raise
     print(f"Found SDL {sdl_version_str}.")
     sdl_version = tuple(int(s) for s in sdl_version_str.split("."))
     if sdl_version < SDL_VERSION_NEEDED: