Fix CheckTypeSize when flags imply shared memory

[m4burns]

This PR fixes emscripten's patched CheckTypeSize CMake module to work when compiler flags imply shared memory use.

Before this change, trying to configure a CMake project that uses check_type_size when compiler flags implied shared memory (e.g. -sWASM_WORKERS) caused an error:

usr/bin/cmake -E cmake_link_script CMakeFiles/cmTC_ae175.dir/link.txt --verbose=1
/.../emcc  -O3 -msimd128 -sWASM_WORKERS  @CMakeFiles/cmTC_ae175.dir/objects1 -o cmTC_ae175.js @CMakeFiles/cmTC_ae175.dir/linkLibs.rsp
error: library_pthread_stub.js: library_pthread_stub.js:11: #error "STANDALONE_WASM does not support shared memories yet"

This PR resolves the issue by changing oformat to bare, which skips the post-link phase. Type size information can still be extracted from the output.

[kripken]

I see we have test_cmake_threads in test/test_other.py. That enables shared memory here:

https://github.com/emscripten-core/emscripten/blob/ea35c8cde53d4691504436300493d60b49ff3744/test/cmake/threads/CMakeLists.txt#L5

Is that not enough to show the problem this PR fixes? (If not, can we add to that test, or add a new one?)

[m4burns]

I'm guessing nothing in that test calls check_type_size - I will try to add a test for this.