Support building using WASI toolchain #394

Update the build-system ensuring the following defines are set in pyconfig.h:

• HAVE_PTHREAD_STUBS
• _WASI_EMULATED_GETPID
• _WASI_EMULATED_PROCESS_CLOCKS
• _WASI_EMULATED_SIGNAL

Related CPython commits:

• python/cpython@a6ca8eee225 ("bpo-46315: Add ifdef HAVE_ feature checks for WASI compatibility (GH-30507)", 2022-01-13)
• python/cpython@4aea656d628 ("bpo-32033: Finalize WASI configure options (GH-32053)", 2022-03-22)
• python/cpython@e62a0dfab2b ("[3.11] gh-95174: Add pthread stubs for WASI (GH-95234) (#95503)", 2022-08-01)

Related issues and pull requests:

• Add support for Python 3.10, 3.11, 3.12 and 3.13 #350
• Add support for building Python 3.11.x #387