And

Yesterday update of Mojave arrived..
Since then I cannot install: rbenv install 2.6.1
(brew install rbenv ruby-build, works)

How the problem can be solved ?
(cleaned the the tree, but doesn't help)

The mesage:

MacBook-Pro-Andrzej:~ andrzej$ rbenv install 2.6.1
ruby-build: use openssl from homebrew
Downloading ruby-2.6.1.tar.bz2...
-> https://cache.ruby-lang.org/pub/ruby/2.6/ruby-2.6.1.tar.bz2
Installing ruby-2.6.1...
ruby-build: use readline from homebrew

BUILD FAILED (OS X 10.14.5 using ruby-build 20190423)

Inspect or clean up the working tree at /var/folders/_b/vr0hsl0168s6rjlyv_lzdyz00000gn/T/ruby-build.20190522082151.1181
Results logged to /var/folders/_b/vr0hsl0168s6rjlyv_lzdyz00000gn/T/ruby-build.20190522082151.1181.log

Last 10 log lines:
compiling ast.c
compiling bignum.c
compiling class.c
compiling compar.c
error: error reading '/dev/fd/8'
1 error generated.
clang: error: unable to remove file: Operation not permitted
dtrace: failed to compile script probes.d: Preprocessor failed to process input program
make: *** [probes.h] Error 1
make: *** Waiting for unfinished jobs....