Debug builds of Binaryen.js (both JS and Wasm) seem to differ from Release builds, in that Debug builds appear to anticipate BigInt integration in the C ABI while Release builds do not.

Compiling the binaryen_js target using -DCMAKE_BUILD_TYPE=Debug fails at the end of compilation during wasm2js invocation:

[100%] Linking CXX executable bin/binaryen_js.js
em++: error: wasm2js does not support WASM_BIGINT
make[3]: *** [CMakeFiles/binaryen_js.dir/build.make:393: bin/binaryen_js.js] Error 1
make[2]: *** [CMakeFiles/Makefile2:363: CMakeFiles/binaryen_js.dir/all] Error 2
make[1]: *** [CMakeFiles/Makefile2:370: CMakeFiles/binaryen_js.dir/rule] Error 2
make: *** [Makefile:190: binaryen_js] Error 2
emmake: error: 'make -j12 binaryen_js' failed (returned 2)

Compiling the binaryen_wasm target using -DCMAKE_BUILD_TYPE=Debug works, but yields a binary where _BinaryenLiteralInt64 expects a BigInt argument, not two number arguments (low and high bits), then failing at runtime when _BinaryenLiteralInt64 is invoked with two number values:

TypeError: Cannot convert [some number] to a BigInt
  at file://path/to/binaryen_wasm.js:745:22

Compiling either using -DCMAKE_BUILD_TYPE=Release produces artifacts that do not assume BigInt integration.

Origin seems to be in CmakeLists.txt, where -sWASM_BIGINT is specified for Debug builds only.