Remove unnecessary append to PLUGINS variable in top-level CMakeLists.txt (#10494)

Summary:
The PLUGINS variable already contains a semicolon separated list of plugins to compile, so there is no need to append the space separated list in ROCKSDB_PLUGINS passed in as compile argument. Removing this unnecessary append now allows CMake based compiles for two or more plugins at a time.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/10494

Reviewed By: hx235

Differential Revision: D38482094

Pulled By: ajkr

fbshipit-source-id: 61565f7cae2717e70a92132c972b25692ce6f0e8

CMakeLists.txt

@@ -1008,7 +1008,6 @@ endif()
 set(ROCKSDB_PLUGIN_EXTERNS "")
 set(ROCKSDB_PLUGIN_BUILTINS "")
 message(STATUS "ROCKSDB PLUGINS TO BUILD ${ROCKSDB_PLUGINS}")
-list(APPEND PLUGINS ${ROCKSDB_PLUGINS})
 foreach(PLUGIN IN LISTS PLUGINS)
   set(PLUGIN_ROOT "${CMAKE_CURRENT_SOURCE_DIR}/plugin/${PLUGIN}/")
   message("including rocksb plugin ${PLUGIN_ROOT}")