Add DESTDIR support to fixup_bundle() call

Upstream-Status: Pending
--- ./cmake/PackageBundle.cmake.orig	2022-09-12 18:06:34.000000000 +0200
+++ ./cmake/PackageBundle.cmake	2022-09-12 18:06:46.000000000 +0200
@@ -19,7 +19,7 @@
     "
         include(BundleUtilities)
         set(BU_CHMOD_BUNDLE_ITEMS TRUE)
-        fixup_bundle(\"\${CMAKE_INSTALL_PREFIX}/../MacOS/openttd\"  \"\" \"\")
+        fixup_bundle(\"\$ENV{DESTDIR}\${CMAKE_INSTALL_PREFIX}/../MacOS/openttd\"  \"\" \"\")
     "
     DESTINATION .
     COMPONENT Runtime)