CMake force install

[hainest]

Sometimes the binaries installed into a separate installation directory do not match the ones in the build directory. Bolo found that

As far as installed binaries not matching built binaries, that is
all due to cmake_install.cmake hacking up binaries to change
rpath and other attributes ... and then not changing the modification
time on the, now different, installed binary.

This behavior occurs if anyone uses an "installed"
testsuite.   If you just run the testsuite in the
build dir, it is not installed, so the rewrite
doesn't occur.

We need to force CMake to always copy the files from the build directory into the install directory