Automate WASM build with a new Python script. The script provides
several build profiles with configure flags for Emscripten flavors
and WASI. The script can detect and use Emscripten SDK and WASI SDK from
default locations or env vars.
``configure`` now detects Node arguments and creates HOSTRUNNER
arguments for Node 16. It also sets correct arguments for
``wasm64-emscripten``.
wasm_assets script did not take the ABIFLAG flag of sysconfigdata into
account.
(cherry picked from commit 7a2cc35e1c)
Co-authored-by: Christian Heimes <christian@python.org>