CPack/RPM: Enable rpm threads during package generation

Previously, `w7.xzdio` only used a single CPU core.
Honor `CPACK_THREADS`: `w7T${CPACK_THREADS}.xzdio` uses the specified
number of threads. `w7T.xzdio` uses all available CPU cores.

Fixes: #25615

Modules/Internal/CPack/CPackRPM.cmake

@@ -1041,7 +1041,11 @@ function(cpack_rpm_generate_package)
        set(CPACK_RPM_COMPRESSION_TYPE_TMP "%define _binary_payload w9.lzdio")
      endif()
      if(CPACK_RPM_COMPRESSION_TYPE STREQUAL "xz")
-       set(CPACK_RPM_COMPRESSION_TYPE_TMP "%define _binary_payload w7.xzdio")
+       if(CPACK_THREADS GREATER "0")
+         set(CPACK_RPM_COMPRESSION_TYPE_TMP "%define _binary_payload w7T${CPACK_THREADS}.xzdio")
+       else()
+         set(CPACK_RPM_COMPRESSION_TYPE_TMP "%define _binary_payload w7T.xzdio")
+       endif()
      endif()
      if(CPACK_RPM_COMPRESSION_TYPE STREQUAL "bzip2")
        set(CPACK_RPM_COMPRESSION_TYPE_TMP "%define _binary_payload w9.bzdio")