[Build] Fix variable name in new build system.

It should have been `SwiftCore_MODULE_TRIPLE`, not
`SwiftCore_SWIFT_MODULE_TRIPLE`.

Author: al45tair

Runtimes/Core/cmake/modules/PlatformInfo.cmake

@@ -45,12 +45,12 @@ set(availability_platform_xros "visionOS")
 set(availability_platform_bridgeos "bridgeOS")
 
 if(NOT SwiftCore_SWIFT_AVAILABILITY_PLATFORM)
-  if(SwiftCore_SWIFT_MODULE_TRIPLE MATCHES ".*-([^-]+)-simulator$")
+  if(SwiftCore_MODULE_TRIPLE MATCHES ".*-([^-]+)-simulator$")
     set(platform "${CMAKE_MATCH_1}")
-  elseif(SwiftCore_SWIFT_MODULE_TRIPLE MATCHES ".*-([^-]+)$")
+  elseif(SwiftCore_MODULE_TRIPLE MATCHES ".*-([^-]+)$")
     set(platform "${CMAKE_MATCH_1}")
   else()
-    message(ERROR "Unable to extract platform name from triple ${SwiftCore_SWIFT_MODULE_TRIPLE}")
+    message(ERROR "Unable to extract platform name from triple ${SwiftCore_MODULE_TRIPLE}")
   endif()
 
   if(availability_platform_${platform})
@@ -64,7 +64,7 @@ if(SwiftCore_VARIANT_MODULE_TRIPLE)
   if(SwiftCore_VARIANT_MODULE_TRIPLE MATCHES ".*-([^-]+)$")
     set(platform "${CMAKE_MATCH_1}")
   else()
-    message(ERROR "Unable to extract platform name from triple ${SwiftCore_SWIFT_MODULE_TRIPLE}")
+    message(ERROR "Unable to extract platform name from triple ${SwiftCore_VARIANT_MODULE_TRIPLE}")
   endif()
 
   if(availability_platform_${platform})