Generalize computing SWIFT_MODULE_TRIPLE

This patch updates the logic for figuring out the Swift module triple
from manually trying to patch something together to just asking the
Swift driver to tell us what it is based on what we're compiling for.

Author: etcwilde

CMakeLists.txt

@@ -63,23 +63,12 @@ endif()
 
 # Determine the module triple.
 if("${SWIFT_HOST_MODULE_TRIPLE}" STREQUAL "")
-  # FIXME: This is a hack. It's all a hack. Windows isn't setting
-  # CMAKE_Swift_COMPILER_TARGET.
+  set(module_triple_command "${CMAKE_Swift_COMPILER}" -print-target-info)
   if(CMAKE_Swift_COMPILER_TARGET)
-    string(REGEX REPLACE "macosx[0-9]+([.][0-9]+)?" "macos" SWIFT_HOST_MODULE_TRIPLE
-      ${CMAKE_Swift_COMPILER_TARGET})
-  elseif("${CMAKE_SYSTEM_NAME}" STREQUAL "Windows")
-    if(CMAKE_SYSTEM_PROCESSOR MATCHES "x86_64|AMD64")
-      set(SWIFT_HOST_MODULE_TRIPLE "x86_64-unknown-windows-msvc")
-    elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "aarch64|ARM64|arm64")
-      set(SWIFT_HOST_MODULE_TRIPLE "aarch64-unknown-windows-msvc")
-    else()
-      message(FATAL_ERROR "Unrecognized architecture for Windows host")
-    endif()
-  else()
-    execute_process(COMMAND ${CMAKE_Swift_COMPILER} -print-target-info OUTPUT_VARIABLE target_info)
-    string(JSON SWIFT_HOST_MODULE_TRIPLE GET ${target_info} target moduleTriple)
+    list(APPEND module_triple_command -target ${CMAKE_Swift_COMPILER_TARGET})
   endif()
+  execute_process(COMMAND ${module_triple_command} OUTPUT_VARIABLE target_info_json)
+  string(JSON SWIFT_HOST_MODULE_TRIPLE GET "${target_info_json}" "target" "moduleTriple")
 endif()
 message(STATUS "Module triple: ${SWIFT_HOST_MODULE_TRIPLE}")