building the jtreg using jdk11.0.18

[Sergey Bylokhov]

Hello,

I would like to know what is our plan to fix all that issues occurred in our "github actions" for 
jdk 11 and jdk 17. The root cause is an issue in the jtreg build script in the "branch-6.1+x" 
branch, see:
https://github.com/openjdk/jtreg/pull/146

So we can integrate that fix to the jtreg/"branch-6.1+x" and then use the next tag in our scripts.
Or we can just update the jtreg to to the latest one:branch-7.1+x

Any objections to bump the version to 7.1.1+1 like the jdk/jdk did?

-- 
Best regards, Sergey.