added sccache commands to build all to test functionality

[Eliasj42]

ci-exactly: windows_x64_msvc

[ScottTodd]

Drive-by comments:

• You don't need to create a pull request to use workflow_dispatch. If your work is still a draft and you aren't yet looking for comments, then you can limit notification noise by just pushing to your branch and triggering.
• I expect that configuring and debugging sccache [in scripts] locally on Windows will be easier than iterating on the github actions workflow. If you've already done that, then great.
• You may want to issue calls directly instead of using build_all.sh, or write a new build_all_windows.sh. The script (https://github.com/iree-org/iree/blob/main/build_tools/cmake/build_all.sh) is mostly plumbing and configuration, which you can bypass when writing a workflow directly. See what the other workflows do, for example:

  iree/.github/workflows/ci_linux_x64_clang.yml

  Lines 50 to 68 in d497571

  	- name: CMake - configure
  	run: |
  	source ./build_tools/cmake/setup_sccache.sh
  	cmake \
  	-G Ninja \
  	-B ${BUILD_DIR} \
  	-DPython3_EXECUTABLE="$(which python3)" \
  	-DCMAKE_BUILD_TYPE=RelWithDebInfo \
  	-DIREE_BUILD_PYTHON_BINDINGS=ON \
  	-DIREE_ENABLE_LLD=ON \
  	-DIREE_ENABLE_ASSERTIONS=ON \
  	-DIREE_BUILD_DOCS=ON \
  	-DIREE_TARGET_BACKEND_WEBGPU_SPIRV=ON
  	- name: CMake - build
  	run: |
  	cmake --build ${BUILD_DIR} -- -k 0
  	cmake --build ${BUILD_DIR} --target install -- -k 0
  	cmake --build ${BUILD_DIR} --target iree-test-deps -- -k 0
  	sccache --show-stats

  (actually, now that I look at that, I think some workflows are missing -DIREE_TARGET_BACKEND_CUDA=ON and -DIREE_TARGET_BACKEND_ROCM=ON 🤔 )

[Eliasj42]

Sorry, I thought it said creating a draft PR didn't send out emails