MDEV-23564: CMAKE failing due to deprecated Apple GSS method

Some GSS-API functions like gss_import_name(), gss_release_buffer()
used in plugin/auth_gssapi and libmariadb/plugins/auth are marked
as deprecated in MacOS starting from  version 10.14+. It results in
extra warnings output on server building.

To eliminate extra warnings the flag '-Wno-deprecated-declarations'
has been added to compiler invocation string for those source
files that invoke deprecated GSS-API functions.

plugin/auth_gssapi/CMakeLists.txt

@@ -18,6 +18,11 @@ ELSE()
    SET(GSSAPI_SERVER gssapi_server.cc)
    SET(GSSAPI_ERRMSG gssapi_errmsg.cc)
 
+   IF(APPLE)
+     SET_SOURCE_FILES_PROPERTIES(
+       ${GSSAPI_CLIENT} ${GSSAPI_SERVER} ${GSSAPI_ERRMSG}
+       PROPERTY COMPILE_FLAGS "-Wno-deprecated-declarations")
+   ENDIF()
    SET(CMAKE_REQUIRED_INCLUDES ${GSSAPI_INCS})
    SET(CMAKE_REQUIRED_LIBRARIES ${GSSAPI_LIBS})
    INCLUDE(CheckCXXSymbolExists)