scan-build report includes subprojects

[amcn]

Hello Meson community,

I recently used Meson's scan-build target to analyze a project's code and I found that the generated scan-build report contained bugs found in code inside several of the subprojects that the project uses. Is this the desired behavior?

I was hoping to be able to use the scan-build target in CI jobs and to raise an error if any bugs were discovered but the presence of these subproject bugs means that the report is never empty. I have some solutions in mind to work around this for my use-case, but I thought I would ask if anyone else has encountered this and if it's the desired behavior first.

Many thanks.

[amcn]

For any future readers, as of the merging of this pull request, the scan-build target now excludes subprojects from its final report.