wasm: enable WASM_BIGINT

JavaScripts's BigInt feature provides support for arbitrary-precision
integers. This makes it possible to represent 64-bit integers; the
standard JS Number type supports 32-bit integers only (or more
accurately 53-bit integers - see Number.MAX_SAFE_INTEGER).

Enable WASM_BIGINT which makes Emscripten map int64_t and uint64_t
to BigInt when interfacing with JavaScript code.

This removes one of the conditions which enables
wasm-emscripten-finalize.

Task-number: QTBUG-103352
Change-Id: Ia70d599daaf34c92695f5a2b61665e0c237e6b95
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
Reviewed-by: Lorn Potter <lorn.potter@gmail.com>
Reviewed-by: David Skoland <david.skoland@qt.io>

cmake/QtWasmHelpers.cmake

@@ -7,7 +7,8 @@ function (qt_internal_setup_wasm_target_properties wasmTarget)
     "SHELL:-s EXPORTED_RUNTIME_METHODS=[UTF16ToString,stringToUTF16,specialHTMLTargets]"
     "SHELL:-s USE_WEBGL2=1"
     "--bind"
-    "SHELL:-s FETCH=1")
+    "SHELL:-s FETCH=1"
+    "SHELL:-s WASM_BIGINT=1")
 
     # Enable MODULARIZE and set EXPORT_NAME, which makes it possible to
     # create application instances using a global constructor function,

mkspecs/wasm-emscripten/qmake.conf

@@ -38,7 +38,8 @@ EMCC_COMMON_LFLAGS += \
     --bind \
     -s FETCH=1 \
     -s MODULARIZE=1 \
-    -s EXPORT_NAME=createQtAppInstance
+    -s EXPORT_NAME=createQtAppInstance \
+    -s WASM_BIGINT=1
 
 # The -s arguments can also be used with release builds,
 # but are here in debug for clarity.