Disable WASM in the test build script for Emscripten.

This makes it more convenient to test because it avoids the need for
the use of emrun.

tests/mal_build_tests_emscripten.bat

-emcc ./mal_test_0.c -o ./bin/mal_test_0_emscripten.html -O3
\ No newline at end of file
+emcc ./mal_test_0.c -o ./bin/mal_test_0_emscripten.html -s WASM=0
\ No newline at end of file