default or selected kernelversion does not have config value CONFIG_PLUGIN_HOSTCC.
Result is shown for kernelversion 6.9.9

CONFIG_PLUGIN_HOSTCC (not configurable)

configname: CONFIG_PLUGIN_HOSTCC

Linux Kernel Configuration
└─>General architecture-dependent options
└─>PLUGIN_HOSTCC
In linux kernel since version 4.2 (release Date: 2015-08-30)  
Host compiler used to build GCC plugins. This can be $(HOSTCXX),
$(HOSTCC), or a null string if GCC plugin is unsupported.