Relative path for CMAKE_INSTALL_LIBDIR broken

[olesenm]

As a workaround or fix for issue #951, now specified -DCMAKE_INSTALL_LIBDIR=lib.
Surprisingly this failed. It only seems to work with an absolute path, contrary to what the cmake docs suggest.

With a relative path, both the fmt and umpire files are installed in the build directory.
To diagnose which files are actually being installed in the wrong directory versus files left behind from the build process itself, I specified -DCMAKE_INSTALL_LIBDIR=mylib instead. These ones are being installed under the build directory:

<build-dir>/mylib/libfmt.a
<build-dir>/mylib/libumpire.a

<build-dir>/mylib/pkgconfig/fmt.pc

<build-dir>/mylib/cmake/fmt/*.cmake
<build-dir>/mylib/cmake/umpire/*.cmake

The real installation gets these:

<prefix-dir>/lib/libcamp.a
<prefix-dir>/lib/cmake/camp/*.cmake

The BLTInstallableMacros.cmake, BLTSetupTargets.cmake, BLTThirdPartyConfigFlags.cmake files are installed both under the cmake/camp as well as the cmake/umpire directories. I just mention that in case it is incorrect or otherwise useful to know.

So the current workaround is obviously to specify libdir as an absolute path and pretend that it is CMAKE_INSTALL_FULL_LIBDIR for now.