Windows build with clang-cl; CI for Windows/ARM64 build (#1538)

## Issues
Needed for: aws/aws-lc-rs#376

## Description
* Updated `CMakeLists.txt` to support a Windows build using `clang-cl`.
* Adds CI build/test of Windows/x64 using clang-cl.
* Adds CI build of Windows/ARM64 using clang-cl. (Currently there are no
runners available for testing Windows/ARM64 executables.)

## Callout
* This change removes debug information by default from the "Release"
build type. Alternatively, one may retain debug information in the
artifacts by adding the `-ggdb` build flag via **CMAKE_C_FLAGS** or by
using the "Relwithdebinfo" or "Debug" build types.

By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache 2.0 license and the ISC license.

.github/workflows/windows-alt.yml

@@ -63,12 +63,64 @@ jobs:
           options: |
             CMAKE_SYSTEM_NAME=Windows \
             CMAKE_SYSTEM_PROCESSOR=x86_64 \
-            CMAKE_BUILD_TOOL=ninja.exe \
+            CMAKE_MAKE_PROGRAM=ninja.exe \
             CMAKE_BUILD_TYPE=Release \
       - name: Build Project
         run: cmake --build ./build --target all
       - name: Run tests
         run: cmake --build ./build --target run_tests
+  clang-cl:
+    if: github.repository_owner == 'aws'
+    strategy:
+      fail-fast: false
+      matrix:
+        target:
+          - x64
+          - x64_arm64
+    runs-on: windows-latest
+    steps:
+      - if: ${{ matrix.target  == 'x64' }}
+        name: Install NASM
+        uses: ilammy/[email protected]
+      - name: Remove wrong clang-cl.exe
+        run:  rm "C:/Program Files/LLVM/bin/clang-cl.exe"
+      - name: Checkout
+        uses: actions/checkout@v4
+      - uses: TheMrMilchmann/setup-msvc-dev@v3
+        with:
+          arch: ${{ matrix.target }}
+      - if: ${{ matrix.target  == 'x64' }}
+        name: Setup CMake
+        uses: threeal/[email protected]
+        with:
+          generator: Ninja
+          c-compiler: clang-cl
+          cxx-compiler: clang-cl
+          options: |
+            CMAKE_CROSSCOMPILING=${{ ((matrix.target  == 'x64') && '0') || '1' }} \
+            CMAKE_SYSTEM_NAME=Windows \
+            CMAKE_SYSTEM_PROCESSOR=x86_64 \
+            CMAKE_BUILD_TYPE=Release \
+      - if: ${{ matrix.target  == 'x64_arm64' }}
+        name: Setup CMake
+        uses: threeal/[email protected]
+        with:
+          generator: Ninja
+          c-compiler: clang-cl
+          cxx-compiler: clang-cl
+          options: |
+            CMAKE_CROSSCOMPILING=1 \
+            CMAKE_SYSTEM_NAME=Windows \
+            CMAKE_SYSTEM_PROCESSOR=ARM64 \
+            CMAKE_C_COMPILER_TARGET=arm64-pc-windows-msvc \
+            CMAKE_ASM_COMPILER_TARGET=arm64-pc-windows-msvc \
+            CMAKE_CXX_COMPILER_TARGET=arm64-pc-windows-msvc \
+            CMAKE_BUILD_TYPE=Release \
+      - name: Build Project
+        run: cmake --build ./build --target all
+      - if: ${{ matrix.target  == 'x64' }}
+        name: Run tests
+        run: cmake --build ./build --target run_tests
   cross-mingw:
     if: github.repository_owner == 'aws'
     runs-on: ubuntu-22.04
@@ -95,4 +147,3 @@ jobs:
       - name: x86_64-w64-mingw32 Build/Test
         run:
           ./tests/ci/run_cross_mingw_tests.sh x86_64 w64-mingw32 "-DCMAKE_BUILD_TYPE=Release"
-

CMakeLists.txt

@@ -347,32 +347,38 @@ if(GCC OR CLANG)
   # TODO(CryptoAlg-759): enable '-Wpedantic' if awslc has to follow c99 spec.
   if(CLANG OR (GCC AND CMAKE_C_COMPILER_VERSION VERSION_GREATER "4.1.3"))
     # GCC 4.1.3 and below do not support all of these flags or they raise false positives.
-    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fvisibility=hidden -Wall -Wextra -Wno-unused-parameter -Werror")
+    if (MSVC)
+      # clang-cl sets different default warnings than clang. It also treats -Wall
+      # as -Weverything, to match MSVC. Instead -W3 is the alias for -Wall.
+      # See http://llvm.org/viewvc/llvm-project?view=revision&revision=319116
+      set(C_CXX_FLAGS "${C_CXX_FLAGS} -W3 -fmsc-version=1900")
+      set(C_CXX_FLAGS "${C_CXX_FLAGS} -Wno-deprecated-declarations")
+    else()
+      set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wextra")
+      set(C_CXX_FLAGS "${C_CXX_FLAGS} -Wall -fvisibility=hidden -fno-common")
+    endif()
     set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wunused -Wcomment -Wchar-subscripts -Wuninitialized -Wshadow")
     set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wwrite-strings -Wformat-security -Wunused-result")
-    set(C_CXX_FLAGS "${C_CXX_FLAGS} -Wvla -Wtype-limits")
+    set(C_CXX_FLAGS "${C_CXX_FLAGS} -Wvla -Wtype-limits -Wno-unused-parameter")
   endif()
+  set(C_CXX_FLAGS "${C_CXX_FLAGS} -Werror -Wformat=2 -Wsign-compare -Wmissing-field-initializers -Wwrite-strings")
 
   if(GCC AND CMAKE_C_COMPILER_VERSION VERSION_GREATER "8")
     # GCC 8.x added a warning called -Wcast-function-type to the -Wextra umbrella.
     set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wno-cast-function-type")
   endif()
 
-  set(C_CXX_FLAGS "${C_CXX_FLAGS} -Werror -Wformat=2 -Wsign-compare -Wmissing-field-initializers -Wwrite-strings")
-  if(MSVC)
-    # clang-cl sets different default warnings than clang. It also treats -Wall
-    # as -Weverything, to match MSVC. Instead -W3 is the alias for -Wall.
-    # See http://llvm.org/viewvc/llvm-project?view=revision&revision=319116
-    set(C_CXX_FLAGS "${C_CXX_FLAGS} -W3 -Wno-unused-parameter -fmsc-version=1900")
-  else()
-    if(EMSCRIPTEN)
-      # emscripten's emcc/clang does not accept the "-ggdb" flag.
-      set(C_CXX_FLAGS "${C_CXX_FLAGS} -g")
+  if(CMAKE_BUILD_TYPE_LOWER STREQUAL "debug" OR CMAKE_BUILD_TYPE_LOWER STREQUAL "relwithdebinfo")
+    if (MSVC)
+      set(C_CXX_FLAGS "${C_CXX_FLAGS} /Zi")
     else()
-      set(C_CXX_FLAGS "${C_CXX_FLAGS} -ggdb")
+      if(EMSCRIPTEN)
+        # emscripten's emcc/clang does not accept the "-ggdb" flag.
+        set(C_CXX_FLAGS "${C_CXX_FLAGS} -g")
+      else()
+        set(C_CXX_FLAGS "${C_CXX_FLAGS} -ggdb")
+      endif()
     endif()
-
-    set(C_CXX_FLAGS "${C_CXX_FLAGS} -Wall -fvisibility=hidden -fno-common")
   endif()
 
   if(MINGW)