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.

deps/OCCT/OCCT.cmake

@@ -1,3 +1,10 @@
+# clang-cl cannot emit IGESAppli_GeneralModule.cxx on ARM64
+# (llvm/llvm-project#62081). cl and clang-cl share an ABI.
+set(_occt_compiler_args "")
+if ("${DEPS_ARCH}" STREQUAL "arm64" AND CMAKE_CXX_COMPILER_ID STREQUAL Clang)
+    set(_occt_compiler_args -DCMAKE_C_COMPILER:STRING=cl -DCMAKE_CXX_COMPILER:STRING=cl)
+endif ()
+
 if(WIN32)
     set(library_build_type "Shared")
 else()
@@ -31,6 +38,7 @@ orcaslicer_add_cmake_project(OCCT
         -DBUILD_MODULE_ModelingAlgorithms=OFF
         -DBUILD_MODULE_ModelingData=OFF
         -DBUILD_MODULE_Visualization=OFF
+        ${_occt_compiler_args}
 )
 
 # add_dependencies(dep_OCCT ${FREETYPE_PKG})

deps/OpenCV/OpenCV.cmake

@@ -10,6 +10,13 @@ else ()
     set(_options "")
 endif ()
 
+# carotene is OpenCV's ARM NEON HAL. It uses M_PI without _USE_MATH_DEFINES
+# and does not compile with clang-cl.
+set(_disable_carotene "")
+if ("${DEPS_ARCH}" STREQUAL "arm64" AND CMAKE_CXX_COMPILER_ID STREQUAL Clang)
+    set(_disable_carotene "-DWITH_CAROTENE=OFF")
+endif ()
+
 if (IN_GIT_REPO)
     set(OpenCV_DIRECTORY_FLAG --directory ${BINARY_DIR_REL}/dep_OpenCV-prefix/src/dep_OpenCV)
 endif ()
@@ -83,5 +90,6 @@ orcaslicer_add_cmake_project(OpenCV
        -DWITH_PROTOBUF=OFF
        -DWITH_WIN32UI=OFF
        -DHAVE_WIN32UI=FALSE
+       ${_disable_carotene}
 )
 

deps/OpenSSL/OpenSSL.cmake

@@ -6,7 +6,7 @@ if(DEFINED OPENSSL_ARCH)
     set(_cross_arch ${OPENSSL_ARCH})
 else()
     if(WIN32)
-        if("${CMAKE_GENERATOR_PLATFORM}" STREQUAL "ARM64")
+        if("${DEPS_ARCH}" STREQUAL "arm64")
             set(_cross_arch "VC-WIN64-ARM")
         else()
             set(_cross_arch "VC-WIN64A")

deps/PNG/PNG.cmake

@@ -1,6 +1,10 @@
 if (APPLE)
     # Only disable NEON extension for Apple ARM builds, leave it enabled for Raspberry PI.
     set(_disable_neon_extension "-DPNG_ARM_NEON=off")
+elseif ("${DEPS_ARCH}" STREQUAL "arm64" AND CMAKE_CXX_COMPILER_ID STREQUAL Clang)
+    # libpng's CMake ignores PNG_ARM_NEON on Windows ARM64 and skips the NEON
+    # sources, but pngpriv.h enables NEON anyway.
+    set(_disable_neon_extension "-DCMAKE_C_FLAGS=/DWIN32 /D_WINDOWS /DPNG_ARM_NEON_OPT=0")
 else ()
     set(_disable_neon_extension "")
 endif ()