MDEV-5026 cannot use system jemalloc

cmake/jemalloc.cmake

@@ -30,14 +30,23 @@ MACRO (USE_BUNDLED_JEMALLOC)
 ENDMACRO()
 
 SET(WITH_JEMALLOC "yes" CACHE STRING
-    "Which jemalloc to use (possible values are 'no', 'bundled', 'yes' (same as bundled)")
-#"Which jemalloc to use (possible values are 'no', 'bundled', 'system', 'yes' (system if possible, otherwise bundled)")
+    "Which jemalloc to use (possible values are 'no', 'bundled', 'system', 'yes' (system if possible, otherwise bundled)")
 
 MACRO (CHECK_JEMALLOC)
   IF(WIN32)
     SET(WITH_JEMALLOC "no")
   ENDIF()
-  IF(WITH_JEMALLOC STREQUAL "bundled" OR WITH_JEMALLOC STREQUAL "yes")
+  IF(WITH_JEMALLOC STREQUAL "system" OR WITH_JEMALLOC STREQUAL "yes")
+    CHECK_LIBRARY_EXISTS(jemalloc malloc_stats_print "" HAVE_JEMALLOC)
+    IF (HAVE_JEMALLOC)
+      SET(LIBJEMALLOC jemalloc)
+    ELSEIF (WITH_JEMALLOC STREQUAL "system")
+      MESSAGE(FATAL_ERROR "system jemalloc is not found")
+    ELSEIF (WITH_JEMALLOC STREQUAL "yes")
+      SET(trybundled 1)
+    ENDIF()
+  ENDIF()
+  IF(WITH_JEMALLOC STREQUAL "bundled" OR trybundled)
     USE_BUNDLED_JEMALLOC()
   ENDIF()
 ENDMACRO()