Update Emscripten SDK from 3.1.28 to 4.0.23 (#1907)

Summary:
Pull Request resolved: #1907

Update the Emscripten SDK used for the JavaScript WASM build from
3.1.28 to 4.0.23. This brings ~2 years of Emscripten improvements
including better WASM codegen and smaller JS glue output.

Required build config changes for Emscripten 4.x compatibility:
- Remove `--memory-init-file 0` (deprecated, no longer accepted)
- Change `TEXTDECODER=0` to `TEXTDECODER=2` (0 is no longer valid)
- Add `EXPORTED_RUNTIME_METHODS=['HEAPF32','HEAP32']` (heap views are
  no longer on Module by default in 4.x)

**Bundle size:**

| Metric | emsdk 3.1.28 | emsdk 4.0.23 | Change |
|---|---|---|---|
| Raw | 115,370 B | 90,219 B | -21.8% |
| Gzip | 42,764 B | 34,445 B | -19.4% |

**Benchmark results (median of 3 runs):**

| Benchmark | 3.1.28 | 4.0.23 | Change |
|---|---|---|---|
| Stack with flex | 9ms | 6ms | similar |
| Align stretch | 5ms | 4ms | similar |
| Nested flex | 4ms | 4ms | same |
| Huge nested layout | 5ms | 4ms | similar |

Reviewed By: cortinico

Differential Revision: D95012856

fbshipit-source-id: b594f1a50626dc6c30b7a934c6146774b74ccfc1

Author: NickGerleman

javascript/CMakeLists.txt

@@ -32,7 +32,6 @@ add_compile_options(${COMPILE_OPTIONS})
 add_link_options(
     ${COMPILE_OPTIONS}
     "SHELL:--closure 1"
-    "SHELL:--memory-init-file 0"
     "SHELL:--no-entry"
     "SHELL:-s ALLOW_MEMORY_GROWTH=1"
     "SHELL:-s ASSERTIONS=0"
@@ -44,12 +43,14 @@ add_link_options(
     "SHELL:-s MODULARIZE=1"
     "SHELL:-s EXPORT_ES6=1"
     "SHELL:-s WASM=1"
-    "SHELL:-s TEXTDECODER=0"
+    "SHELL:-s TEXTDECODER=2"
     "SHELL:-s SUPPORT_BIG_ENDIAN=1"
     # SINGLE_FILE=1 combined with ENVIRONMENT='web' creates code that works on
     # both bundlders and Node.
     "SHELL:-s SINGLE_FILE=1"
-    "SHELL:-s ENVIRONMENT='web'")
+    "SHELL:-s ENVIRONMENT='web'"
+    "SHELL:-s EXPORTED_RUNTIME_METHODS=['HEAPF32','HEAP32']"
+    "SHELL:-Wl,--export-dynamic")
 
 add_library(yogaObjLib OBJECT ${YOGA_SOURCES} ${BRIDGE_SOURCES})
 

javascript/just.config.cjs

@@ -137,7 +137,7 @@ function runBenchTask() {
   };
 }
 
-const emsdkVersion = '3.1.28';
+const emsdkVersion = '4.0.23';
 const emsdkPath = path.join(__dirname, '.emsdk');
 const emsdkBin = path.join(
   emsdkPath,