Fixed make install

[LiamBindle]

This change fixes make install. The "install" locations are controlled by the RUNDIR CMake variable. The behaviour is

• "install" (i.e. copy) location(s) for geos is controlled by -DRUNDIR= with CMake
• If RUNDIR is not empty (empty means "" which is its default value), then geos will be "installed" to each directory in RUNDIR
• RUNDIR can be empty ("" which is its default value), a single directory (relative or absolute), or multiple directories (relative or absolute, directories are semicolon separated as is standard for CMake)

Note that CMAKE_PREFIX_PATH is completely ignored now. This isn't ideal, but it cant be a list and so it doesn't work well for specifying run directories to install geos to (since someone might want to install geos to multiple run directories from a single build).

[lizziel]

Could you give a few usage examples? I can pull this in shortly, as soon as it finished the quick build.

[LiamBindle]

For sure! For example

When RUNDIR is empty

By default RUNDIR is initialized to empty (""). This is equivalent to

cmake . -DRUNDIR=""

With this make install does nothing. Instead, users would use cp to copy bin/geos to their run directory.

When RUNDIR has 1 path

If instead the user wants make install to copy /path/to/rundir1 they would do

cmake . -DRUNDIR="/path/to/rundir1"

With this make install copies bin/geos to /path/to/rundir1.

When RUNDIR has multiple paths

Say a user wants to build GCHP and use the same executable in /path/to/rundir1, /path/to/rundir2, and /path/to/rundir3. Then they would do

cmake . -DRUNDIR="/path/to/rundir1;/path/to/rundir2;/path/to/rundir3"

Then, doing make install would copy bin/geos to all three run directories.

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Note that it's perfectly okay to update RUNDIR after building. Subsequent make install will copy geos to the updated run directories.

Today I was working on the quickstart guide, and this is mostly just a polishing so that we don't have to say e.g. "after compiling, copy the geos executable in build/bin to your run directories". Note that an initial draft of the quickstart guide is live: https://gchp.readthedocs.io/en/latest/ (or should be within ~20 minutes).