[CMake] install(EXPORT ...) includes target "B" which requires target "A" that is not in the export set

[Nico Schlömer]

Hi all,

One of my projects contains two libraries libA and libB, where libB
depends on libA, and both are exporting their configuration through
the usual `INSTALL(EXPORT ...)` mechanisms.
I'm getting errors of the type
```
CMake Error: install(EXPORT "SEACASNemesis-exports" ...) includes
target "nemesis" which requires target "exodus" that is not in the
export set.
```
now, and I'm not quite sure what they mean. Do all of my export files
have to be self-contained?
In other projects of mine, CMake was happy to produce target files with
```
set_target_properties(teuchosnumerics PROPERTIES
  IMPORTED_LINK_INTERFACE_LIBRARIES_NONE
"B;A;/usr/lib/liblapack.so;/usr/lib/libblas.so"
  IMPORTED_LOCATION_NONE "${_IMPORT_PREFIX}/lib/x86_64-linux-gnu/libB.so.11.11"
  IMPORTED_SONAME_NONE "libB.so.11"
  )
```
without A appearing in the same target file.

Cheers,
Nico