build: use clang-cl for Windows CI builds (faster slicing and faster builds) (#15428)

* ci: build the Windows x64 dependencies and slicer with clang-cl

Passes -l -x from the Windows jobs, using the clang-cl and Ninja options
added in #15373. Ninja runs each dependency's build step as a plain command,
so the jobs set up a VC environment for OpenSSL's nmake. arm64 stays on MSVC
for now.

The deps cache key gains the compiler, so windows-x64 becomes
windows-x64-clang and windows-arm64 becomes windows-arm64-msvc.

* deps: select OpenSSL's ARM64 target from DEPS_ARCH

CMAKE_GENERATOR_PLATFORM is only set by -A, which Ninja never receives, so
the Ninja build selected the x64 target on ARM64. DEPS_ARCH is derived from
CMAKE_SYSTEM_PROCESSOR and is already independent of the generator.

* ci: build the Windows ARM64 dependencies and slicer with clang-cl

Three dependencies need handling first. libpng and OpenCV each build an ARM
SIMD path that does not compile with clang-cl, so those paths are off; PNG
already had the same opt-out for Apple ARM. OCCT is built with cl, since
clang-cl cannot emit one of its large generated files and there is no option
to turn that off. All three are gated to Windows ARM64 with clang.

.github/workflows/build_check_cache.yml

@@ -9,6 +9,10 @@ on:
       arch:
         required: false
         type: string
+      compiler:
+        required: false
+        type: string
+        default: msvc
       build-deps-only:
         required: false
         type: boolean
@@ -33,10 +37,10 @@ jobs:
       - name: set outputs
         id: set_outputs
         env:
-          # Keep macOS/Windows cache keys architecture-specific. amd64 Linux passes
-          # no arch (key stays 'linux-clang', preserving the existing cache);
-          # aarch64 gets its own 'linux-clang-aarch64' key.
-          cache-os: ${{ runner.os == 'macOS' && format('macos-{0}', inputs.arch) || (runner.os == 'Windows' && format('windows-{0}', inputs.arch) || format('linux-clang{0}', inputs.arch && format('-{0}', inputs.arch) || '')) }}
+          # Anything that changes how the tree is built belongs in the key, or a job
+          # restores one it cannot use. Linux amd64 passes no arch deliberately, so
+          # 'linux-clang' keeps the cache it already has.
+          cache-os: ${{ runner.os == 'macOS' && format('macos-{0}', inputs.arch) || (runner.os == 'Windows' && format('windows-{0}-{1}', inputs.arch, inputs.compiler) || format('linux-clang{0}', inputs.arch && format('-{0}', inputs.arch) || '')) }}
           # ARM64 builds use the build-arm64 tree (see build_release_vs.bat); x64/other use build.
           dep-folder-name: ${{ runner.os == 'macOS' && format('/{0}', inputs.arch) || (runner.os == 'Windows' && inputs.arch == 'arm64') && '-arm64/OrcaSlicer_dep' || '/OrcaSlicer_dep' }}
           output-cmd: ${{ runner.os == 'Windows' && '$env:GITHUB_OUTPUT' || '"$GITHUB_OUTPUT"'}}
@@ -62,6 +66,7 @@ jobs:
       valid-cache: ${{ needs.check_cache.outputs.valid-cache == 'true' }}
       os: ${{ inputs.os }}
       arch: ${{ inputs.arch }}
+      compiler: ${{ inputs.compiler }}
       build-deps-only: ${{ inputs.build-deps-only }}
       force-build: ${{ inputs.force-build }}
     secrets: inherit