I have made a few tries and found a few workarounds to my svn 12294 problem (Am I alone ?).
For svn 12295, no changes ... normal.
If I use my previous working 12292 working version (the one built incrementally), it works as said before.
If I only replace codeblocks.exe in my svn 12295 build, the one found in my working svn 12292, it works too. Certainly not a good idea to mix versions, but it was just to try.
I also tried an other compiler found on winlibs.
I first tried the latest version (release 7) to build C::B 12295, but had the same trouble when launching a new compilation of every soft (my own, but not only). Not so surprising because they probably share the same sources versions if I look at the dates.
Then I tried a previous compiler set version (release 4), also found on Winlibs, generated in 2020/08, to build C::B 12295. Here, the resulting C::B works as expected.
So, I suppose that in C::B, and more precisely in the executable codeblocks.exe, there is something which is not correctly compiled with those recent compiler versions (Msys2 and/or latest winlibs), maybe somewhere when preparing the call to the compiler. Bug in C::B or in the compiler itself, I don't know.