CMake: header installation directory

[nielsvd]

Hi Gianluca,

I believe this line should be:

$<INSTALL_INTERFACE:${BLASFEO_HEADERS_INSTALLATION_DIRECTORY}>)

instead of:

$<INSTALL_INTERFACE:include/blasfeo/include>)

Best, Niels

[giaf]

Thanks Niels!

The cmake build system has been edited by tons of people, this piece of code looks like the hard-coded location of headers in acados.
I'll fix it, thanks for spotting!