Disabling signals is broken in V3

[petermost]

Describe the bug
It is not possible to disable signals in Catch2 V3 when it is prebuild into a static library.

Expected behavior
In V2 it was possible to disable signals/SEH with defining CATCH_CONFIG_NO_POSIX_SIGNALS and CATCH_CONFIG_NO_WINDOWS_SEH because it was a header only library. It would be nice if this would also possible for V3 without the need to build the library yourself.

Reproduction steps
The problem is also described here:
#1295 (comment)
The example code is trying to disable the signals like in V2, but in V3 these defines need to be defined when building the library itself.

Platform information:

• OS: Linux / Windows
• Catch version: v3

Additional context
I'm maintaining a fork of Sourcetrail which contains tests for JNI/JVM function calls. The JVM is internally using signals and this will lead to test failures because Catch2 intercepts these signals and reports a SIGSEGV.

I probably don't need to mention this, but this issue might become more urgent when Debian/Ubuntu starts to deploy a prebuild Catch2 V3 via their repositories.