Fix generate_version_cpp target

[rurban]

Create version.cpp in the src dir, where it is picked up.
And not in the build dir, where it is ignored.

Repro: check bin/cbmc --version for the correct version.
Or just strings src/util/CMakeFiles/util.dir/version.cpp.o

[codecov]

Codecov Report

Merging #6014 (931d782) into develop (ffd00f0) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop    #6014   +/-   ##
========================================
  Coverage    74.23%   74.23%           
========================================
  Files         1444     1444           
  Lines       157309   157309           
========================================
  Hits        116781   116781           
  Misses       40528    40528           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 5b8a3d2...931d782. Read the comment docs.

[TGWDB]

@rurban The generated version.cpp file should be in a build directory not a source directory (as this PR seems to specify). Can you provide a little more clarity on what the problem this fix is meant to solve is? Note that it appears the current build process picks up the version number correctly.

P.S. This will conflict with #6015 , so if there does need to be a fix to the version.cpp location please separate this from a version number change.

[thomasspriggs]

The current build system is correct. A version mismatch was shown in the file names / release page for 5.26.1 due to a test of the github action which performs the release packaging, without us doing the corresponding update to config.inc. The current version is intended to be 5.26.0, not 5.26.1 and we have removed the invalid 5.26.1 release from the release page.