force jemalloc to be used in release rpm/deb builds

unless explicitly overruled with -DWITH_JEMALLOC=no

cmake/build_configurations/mysql_release.cmake

@@ -97,11 +97,13 @@ ELSEIF(RPM)
   SET(WITH_ZLIB system CACHE STRING "")
   SET(CHECKMODULE /usr/bin/checkmodule CACHE FILEPATH "")
   SET(SEMODULE_PACKAGE /usr/bin/semodule_package CACHE FILEPATH "")
+  SET(WITH_JEMALLOC "yes" CACHE STRING "")
 ELSEIF(DEB)
   SET(WITH_SSL system CACHE STRING "")
   SET(WITH_ZLIB system CACHE STRING "")
   SET(WITH_LIBWRAP ON)
   SET(HAVE_EMBEDDED_PRIVILEGE_CONTROL ON)
+  SET(WITH_JEMALLOC "yes" CACHE STRING "")
 ELSE()
   SET(WITH_SSL bundled CACHE STRING "")
   SET(WITH_PCRE bundled CACHE STRING "")