gh-84461: Build Emscripten with WASM BigInt support (GH-94219)

(cherry picked from commit e69306f)

Co-authored-by: Christian Heimes <christian@python.org>

Author: miss-islington

Tools/wasm/README.md

@@ -98,9 +98,11 @@ popd
 ```
 
 ```shell
-node --experimental-wasm-threads --experimental-wasm-bulk-memory builddir/emscripten-node/python.js
+node --experimental-wasm-threads --experimental-wasm-bulk-memory --experimental-wasm-bigint builddir/emscripten-node/python.js
 ```
 
+(``--experimental-wasm-bigint`` is not needed with recent NodeJS versions)
+
 # wasm32-emscripten limitations and issues
 
 Emscripten before 3.1.8 has known bugs that can cause memory corruption and

configure

@@ -2028,6 +2028,9 @@ AS_CASE([$ac_sys_system],
     dnl Start with 20 MB and allow to grow
     AS_VAR_APPEND([LDFLAGS_NODIST], [" -sALLOW_MEMORY_GROWTH -sTOTAL_MEMORY=20971520"])
 
+    dnl map int64_t and uint64_t to JS bigint
+    AS_VAR_APPEND([LDFLAGS_NODIST], [" -sWASM_BIGINT"])
+
     dnl Include file system support
     AS_VAR_APPEND([LDFLAGS_NODIST], [" -sFORCE_FILESYSTEM -lidbfs.js -lnodefs.js -lproxyfs.js -lworkerfs.js"])