I just found that some warnings from a tool I run in a custom command did not get reported in my cdash build while I was seeing them in my local build.
It turns out the warning lines start with warning: , but the built-in regexes include a bunch of variation with various prefixes and case-sensitive patterns except this one (lower case, no prefix). The same applies for error:
To be honest, when I opened https://gitlab.kitware.com/cmake/cmake/-/blob/master/Source/CTest/cmCTestBuildHandler.cxx I got a bit scared 
I’m not sure I want to touch it to add what seems, to me, to be a regex pattern I would expect to be built-in. Before I open an issue, does someone has information on why this pattern is not in the built-in list?