Clean up CMake

Use Case

Building svFSIplus.

Problem

While slogging through the CMake code to rename svFSIplus I've realized that the CMake code is much more complicated than it needs to be.

It seems that the CMake code that was taken from svFSI was itself copied over from svSolver which was copied from SimVascular (?).

For example Externals: there are no externals and yet there is a directory for this with a CMakeLists.txt file with the comments

#-----------------------------------------------------------------------------
# This is SimVascular's CMakeLists.txt for downloading/building the externals
# needed for SimVacular. Pre-built binaries are only available for certain
# versions of the libraries on certain operating systems. To build your own,

I'm sure that it should not take 3000 lines of CMake code to build a simple application using a few internal packages.

Solution

Simplify the CMake code.

Alternatives considered

Don't simplify the CMake code.

Additional context

No response

Code of Conduct

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