Fix the dependency by making the stamp an actual (yet empty/no-op)
header file which is included by all generated source file. This way, we
ensure that meson rebuild .o files when the .pdb sources are changed.
This is the second solution proposed by eli-schwartz here:
https://github.com/mesonbuild/meson/issues/10196#issuecomment-1080053413
The build now successfully build the PDB files into the source folder
itself. Unfortunately it seems I can't get meson dependencies to work
properly, once more! I added a "sources" argument to the relevant
library() or static_library() but it still uses old versions to build
these. E.g. if I add an error on purpose to a pdb file, the next build
still passes, yet the second-next fails (as it should have before).
Note that I even tested a declare_dependency() with just the "sources"
arguments, because it says "sources to add to targets (or generated
header files that should be built before sources including them are
built)" (so I assume it means that it should be trigger a rebuild,
otherwise it's useless) but it's just not working. I'll investigate
more.
Still going with this for now, because at least generating the PDB
source was a big miss until now. But we should