[client] windows: add native clang-cl build

Build the Windows client against the MSVC ABI while retaining clang
language support. Use vcpkg for ANGLE and libsamplerate, and build
MsQuic with its bundled static OpenSSL.

client/cmake/FindANGLE.cmake

@@ -42,6 +42,18 @@ find_package_handle_standard_args(ANGLE
     ANGLE_GLESV2_LIBRARY
 )
 
+if(ANGLE_FOUND AND MSVC)
+  foreach(_ANGLE_LIBRARY IN ITEMS
+      "${ANGLE_EGL_LIBRARY}"
+      "${ANGLE_GLESV2_LIBRARY}")
+    if(_ANGLE_LIBRARY MATCHES "\\.(a|dll\\.a)$")
+      message(FATAL_ERROR
+        "The clang-cl client requires MSVC-ABI ANGLE .lib files; found "
+        "${_ANGLE_LIBRARY}")
+    endif()
+  endforeach()
+endif()
+
 mark_as_advanced(
   ANGLE_EGL_INCLUDE_DIR
   ANGLE_GLES_INCLUDE_DIR
@@ -68,3 +80,4 @@ endif()
 
 unset(_ANGLE_HINTS)
 unset(_ANGLE_FIND_POLICY)
+unset(_ANGLE_LIBRARY)

client/cmake/FindSampleRate.cmake

@@ -27,6 +27,13 @@ find_package_handle_standard_args(SampleRate
     SampleRate_LIBRARY
 )
 
+if(SampleRate_FOUND AND MSVC AND
+    SampleRate_LIBRARY MATCHES "\\.(a|dll\\.a)$")
+  message(FATAL_ERROR
+    "The clang-cl client requires an MSVC-ABI samplerate .lib; found "
+    "${SampleRate_LIBRARY}")
+endif()
+
 mark_as_advanced(
   SampleRate_INCLUDE_DIR
   SampleRate_LIBRARY