[cmake] properly invalidate tzdb cache; require matching version (#346)

Signed-off-by: crueter <crueter@eden-emu.dev>
Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/346
Reviewed-by: CamilleLaVey <camillelavey99@gmail.com>

externals/nx_tzdb/CMakeLists.txt

@@ -32,10 +32,9 @@ if (CMAKE_SYSTEM_NAME STREQUAL "Windows" OR ANDROID)
 endif()
 
 set(NX_TZDB_VERSION "250725")
+set(NX_TZDB_ROMFS_DIR "${CPM_SOURCE_CACHE}/nx_tzdb")
 
-set(NX_TZDB_ROMFS_DIR "${CPM_SOURCE_CACHE}/nx_tzdb/")
-
-if ((NOT CAN_BUILD_NX_TZDB OR YUZU_DOWNLOAD_TIME_ZONE_DATA) AND NOT EXISTS ${NX_TZDB_ROMFS_DIR})
+if ((NOT CAN_BUILD_NX_TZDB OR YUZU_DOWNLOAD_TIME_ZONE_DATA) AND NOT EXISTS ${NX_TZDB_ROMFS_DIR}/${NX_TZDB_VERSION})
     message(STATUS "Downloading time zone data...")
     AddJsonPackage(tzdb)
 elseif (CAN_BUILD_NX_TZDB AND NOT YUZU_DOWNLOAD_TIME_ZONE_DATA)