Add compatibility check between target CPU vs Skia CPU

This should prevent several linking issues reported only because now
MSVC includes one developer prompt shortcut on Windows (to start the
x86 version) and it's quite common to use the Skia x64 version by
default.

Related to:
aseprite/aseprite#4076
aseprite/aseprite@4f3cf93
aseprite/aseprite#2501 (comment)
aseprite/aseprite#4074 (comment)
aseprite/aseprite#4122 (comment)

cmake/FindSkia.cmake

@@ -39,6 +39,35 @@ endif()
 # SkShaper module + freetype + harfbuzz + zlib
 find_library(SKSHAPER_LIBRARY skshaper PATH "${SKIA_LIBRARY_DIR}")
 
+# Check that Skia is compiled for the same CPU architecture
+if(WIN32 AND
+    MSVC AND
+    NOT "${MSVC_C_ARCHITECTURE_ID}" EQUAL "" AND
+    EXISTS "${SKIA_LIBRARY_DIR}/args.gn" )
+  file(READ "${SKIA_LIBRARY_DIR}/args.gn" SKIA_ARGS_GN)
+  string(REGEX MATCH "target_cpu *=[ \"]*([^ \"]*)" skia_target_cpu_line "${SKIA_ARGS_GN}")
+
+  if(NOT "${skia_target_cpu_line}" EQUAL "")
+    # TODO We should say "laf" instead of "Aseprite", but for clarity
+    #      with Aseprite users we just say "Aseprite"
+    set(skia_target_cpu "${CMAKE_MATCH_1}")
+    string(TOLOWER "${MSVC_C_ARCHITECTURE_ID}" aseprite_target_cpu)
+
+    if(NOT "${aseprite_target_cpu}" STREQUAL "${skia_target_cpu}")
+      message(FATAL_ERROR
+        "----------------------------------------------------------------------"
+        "                        INCOMPATIBILITY ERROR "
+        "----------------------------------------------------------------------\n"
+        " The specified Skia library (${SKIA_LIBRARY_DIR}) is compiled\n"
+        " for ${skia_target_cpu} CPU arch but Aseprite is being targeted for ${aseprite_target_cpu} CPU arch.\n"
+        " \n"
+        " Change Skia to the ${aseprite_target_cpu} version, or start the developer prompt for ${skia_target_cpu}:\n"
+        "   https://docs.microsoft.com/en-us/dotnet/framework/tools/developer-command-prompt-for-vs\n"
+        "----------------------------------------------------------------------")
+    endif()
+  endif()
+endif()
+
 # Check that if Skia is compiled with libc++, we use -stdlib=libc++
 if(UNIX AND NOT APPLE AND EXISTS "${SKIA_LIBRARY_DIR}/args.gn")
   file(READ "${SKIA_LIBRARY_DIR}/args.gn" SKIA_ARGS_GN)