Ah - in re-reading what I said, perhaps I wasn't clear.
If compiling an extension produces *.la files then these are included in the *-dev extension.
In the case of the latest libdrm, it was compiled with meson/ninja, which does not produce any *.la files and thus they were not included in libdrm-dev.
In the particular case of libdrm, I believe it could have been compiled with autotools to produce *.la files, but many other extensions like, for example, atk no longer give the choice.
The above being the case, if *.la files are required, they will need to be taken from the most recent *-dev extension still containing them and copied into the root file system. The *.la files used in this way might need adjustment to match the most recent version of the library concerned.
Many source code packages are transitioning away from autotools, which means that missing *.la files are going to be an issue for some time to come.