I had to re-install MSYS2 and then ran pacman-Syu and siril-deps.sh. Then I cloned the Siril repo and then ran the build setup as I have always done. This gave an error from C:\msys64\home\hairbear\siril\subprojects\librtprocess\CMakeLists.txt. This error has been caused because of a policy change in Cmake version 4.4 onwards regarding the interpretation of backslash as escape (policy CMP0219). I have fixed this by adding the following to the start of CMakeLists.txt …
cmake_policy(SET CMP0219 NEW)
This may or may not be the correct way of fixing this but it’s worked for me.
Regards
Ray Alker.