Eclipse-CS does not refresh Checkstyle's External Resource list

While working on https://github.com/checkstyle/eclipse-cs/issues/454 ,

I noticed when I changed the regular expression header file and did a clean build to re-run Checkstyle, Eclipse-CS kept using the old header file not matter what I did to try to get it to see the new one.

Checkstyle did not recognize the new header file changes until I re-saved the Configuration file, even though it had no more changes at that point.

It seems to me Eclipse-CS is caching something in memory to avoid having Checkstyle recreate the config in memory for each run and is causing issues when it doesn't see something as changed.

Checkstyle's External Resource Info: https://checkstyle.org/writingchecks.html#Declare_check.27s_external_resource_locations