Trigger build before debug

[ilg-ul]

Discussed in #32

^{Originally posted by grigorig May 3, 2022}
It would be very useful to be able to ensure that the executable is built and up to date before a debug session is started, e.g. with the Cortex Debug extension.
The "CMake Tools" extension allows this by referring to the executable via variable expansion, e.g. you specify "executable": "${command:cmake.launchTargetPath}", in the debug configuration. When the variable is expanded, this will implicitly launch a build before debugging is started. I don't see such a feature in the xPack extension, but I think it would be very useful.