This seems like a bug, or at least an exception warranting a warning message. If I already have an operating CMake build but then attempt a "developer override" by ``` cmake -G .. -S.. -B.. -DFETCHCONTENT_SOURCE_DIR_MYDEP=<bad folder> ``` the subsequent cmake --build and cmake --install will forget that MYDEP even exists (kinda' makes sense since FetchContent doesn't find a CMakeLists.txt for MYDEP). The `<bad folder>` in this case is a path that simply doesn't exist. The evidence for failure is that MYDEP fails to show up in the lines of `[ xx%] Built target XXX` emitted by --build. More evidence is `--install .. --component mydep` fails to emit anything beyond the 1st line `-- Install configuration:`. I'm using CMake 3.16 on Win10/Pro/64.