[3.14] gh-133600: Move config.site-wasm32-emscripten into the emscripten folder (GH-136934) (#136956)

Reorganises the large Emscripten-specific file into the Emscripten folder.
(cherry picked from commit bbe589f93c)

Co-authored-by: Hood Chatham <roberthoodchatham@gmail.com>

Tools/wasm/emscripten/__main__.py

@@ -186,7 +186,7 @@ def make_emscripten_libffi(context, working_dir):
 def configure_emscripten_python(context, working_dir):
     """Configure the emscripten/host build."""
     config_site = os.fsdecode(
-        CHECKOUT / "Tools" / "wasm" / "config.site-wasm32-emscripten"
+        EMSCRIPTEN_DIR / "config.site-wasm32-emscripten"
     )
 
     emscripten_build_dir = working_dir.relative_to(CHECKOUT)

Tools/wasm/emscripten/config.site-wasm32-emscripten

@@ -0,0 +1,104 @@
+# config.site override for cross compiling to wasm32-emscripten platform
+#
+# CONFIG_SITE=Tools/wasm/emscripten/config.site-wasm32-emscripten \
+#     emconfigure ./configure --host=wasm32-unknown-emscripten --build=...
+#
+# Written by Christian Heimes <christian@python.org>
+# Partly based on pyodide's pyconfig.undefs.h file.
+#
+
+# cannot be detected in cross builds
+ac_cv_buggy_getaddrinfo=no
+
+# Emscripten has no /dev/pt*
+ac_cv_file__dev_ptmx=no
+ac_cv_file__dev_ptc=no
+
+# new undefined symbols / unsupported features
+ac_cv_func_posix_spawn=no
+ac_cv_func_posix_spawnp=no
+ac_cv_func_eventfd=no
+ac_cv_func_memfd_create=no
+ac_cv_func_prlimit=no
+
+# unsupported syscall, https://github.com/emscripten-core/emscripten/issues/13393
+ac_cv_func_shutdown=no
+
+# The rest is based on pyodide
+# https://github.com/pyodide/pyodide/blob/main/cpython/pyconfig.undefs.h
+
+ac_cv_func_epoll_create=no
+ac_cv_func_epoll_create1=no
+ac_cv_header_linux_vm_sockets_h=no
+ac_cv_func_socketpair=no
+ac_cv_func_sigaction=no
+
+# symlinkat is implemented, but fails
+ac_cv_func_symlinkat=no
+
+# lchmod/lchown are implemented, but fail with ENOTSUP.
+ac_cv_func_lchmod=no
+ac_cv_func_lchown=no
+
+# geteuid / getegid are stubs and always return 0 (root). The stub breaks
+# code that assume effective user root has special permissions.
+ac_cv_func_geteuid=no
+ac_cv_func_getegid=no
+ac_cv_func_seteuid=no
+ac_cv_func_setegid=no
+ac_cv_func_getresuid=no
+ac_cv_func_getresgid=no
+ac_cv_func_setresuid=no
+ac_cv_func_setresgid=no
+
+# Syscalls not implemented in emscripten
+# [Errno 52] Function not implemented
+ac_cv_func_preadv2=no
+ac_cv_func_preadv=no
+ac_cv_func_pwritev2=no
+ac_cv_func_pwritev=no
+ac_cv_func_pipe2=no
+ac_cv_func_nice=no
+ac_cv_func_setpriority=no
+ac_cv_func_setitimer=no
+# unsupported syscall: __syscall_prlimit64
+ac_cv_func_prlimit=no
+# unsupported syscall: __syscall_getrusage
+ac_cv_func_getrusage=no
+ac_cv_func_posix_fallocate=no
+
+# Syscalls that resulted in a segfault
+ac_cv_func_utimensat=no
+ac_cv_header_sys_ioctl_h=no
+
+# sockets are supported, but only AF_INET / AF_INET6 in non-blocking mode.
+# Disable AF_UNIX and AF_PACKET support, see socketmodule.h.
+ac_cv_header_sys_un_h=no
+ac_cv_header_netpacket_packet_h=no
+
+# aborts with bad ioctl
+ac_cv_func_openpty=no
+ac_cv_func_forkpty=no
+
+# mkfifo and mknod are broken, create regular file
+ac_cv_func_mkfifo=no
+ac_cv_func_mkfifoat=no
+ac_cv_func_mknod=no
+ac_cv_func_mknodat=no
+
+# always fails with permission or not implemented error
+ac_cv_func_getgroups=no
+ac_cv_func_setgroups=no
+ac_cv_func_setresuid=no
+ac_cv_func_setresgid=no
+
+# Emscripten does not support hard links, always fails with errno 34
+# "Too many links". See emscripten_syscall_stubs.c
+ac_cv_func_link=no
+ac_cv_func_linkat=no
+
+# Emscripten's faccessat does not accept AT_* flags.
+ac_cv_func_faccessat=no
+
+# alarm signal is not delivered, may need a callback into the event loop?
+ac_cv_func_alarm=no