pythongh-95853: Multiple ops and debug for wasm_build.py

- `wasm_build.py` now supports multiple operations.
- only `build` (default) performs auto-building
- new ops `configure` and `compile`.
- better help
- `repl` starts `wasm_webserver` and opens browser repl
- `test` and `hostrunnertest` now support custom testopts

Author: tiran

Makefile.pre.in

@@ -1718,6 +1718,10 @@ buildbottest: all
 		fi
 		$(TESTRUNNER) -j 1 -u all -W --slowest --fail-env-changed --timeout=$(TESTTIMEOUT) $(TESTOPTS)
 
+# Like testall, but run Python tests with HOSTRUNNER directly.
+hostrunnertest: all
+	$(RUNSHARED) $(HOSTRUNNER) ./$(BUILDPYTHON) -m test -u all $(TESTOPTS)
+
 pythoninfo: all
 		$(RUNSHARED) $(HOSTRUNNER) ./$(BUILDPYTHON) -m test.pythoninfo
 

Tools/wasm/README.md

@@ -1,11 +1,16 @@
 # Python WebAssembly (WASM) build
 
-**WARNING: WASM support is highly experimental! Lots of features are not working yet.**
+**WARNING: WASM support is still experimental! Lots of features are not working yet.**
 
 This directory contains configuration and helpers to facilitate cross
-compilation of CPython to WebAssembly (WASM). For now we support
-*wasm32-emscripten* builds for modern browser and for *Node.js*. WASI
-(*wasm32-wasi*) is work-in-progress
+compilation of CPython to WebAssembly (WASM). Python supports Emscripten
+(*wasm32-emscripten*) and WASI (*wasm32-wasi*) targets. Emscripten builds
+run in modern browsers and JavaScript runtimes like *Node.js*. WASI builds
+use WASM runtimes such as *wasmtime*.
+
+Users and developers are encouraged to use the script
+`Tools/wasm/wasm_build.py`. The tool automates the build process and provides
+assistance with installation of SDKs.
 
 ## wasm32-emscripten build
 
@@ -17,7 +22,7 @@ access the file system directly.
 
 Cross compiling to the wasm32-emscripten platform needs the
 [Emscripten](https://emscripten.org/) SDK and a build Python interpreter.
-Emscripten 3.1.8 or newer are recommended. All commands below are relative
+Emscripten 3.1.19 or newer are recommended. All commands below are relative
 to a repository checkout.
 
 Christian Heimes maintains a container image with Emscripten SDK, Python
@@ -471,6 +476,8 @@ ln -srf -t /usr/local/bin/ ~/.wasmtime/bin/wasmtime
 
 ### WASI debugging
 
-* ``wasmtime run -g`` generates debugging symbols for gdb and lldb.
+* ``wasmtime run -g`` generates debugging symbols for gdb and lldb. The
+  feature is currently broken, see
+  https://github.com/bytecodealliance/wasmtime/issues/4669
 * The environment variable ``RUST_LOG=wasi_common`` enables debug and
   trace logging.