This adds a variable to the library and binary installation directory so they can be easily overridden on command line invocation of cmake.
I'm not sure about other distribution ecosystems, but in Fedora/RHEL/CentOS the cmake rpm macros set LIB_INSTALL_DIR depending on target architecture, so this would place the shared object(s) in the correct directories (currently they are placed in ${prefix}/lib which might be wrong in most cases, since nowadays it's most likely ${prefix}/lib64).
Note that this leaves the default values untouched just as they were before (both default to 'lib') if the variables are not set.
This adds a variable to the library and binary installation directory so they can be easily overridden on command line invocation of cmake. I'm not sure about other distribution ecosystems, but in Fedora/RHEL/CentOS the cmake rpm macros set LIB_INSTALL_DIR depending on target architecture, so this would place the shared object(s) in the correct directories (currently they are placed in ${prefix}/lib which might be wrong in most cases, since nowadays it's most likely ${prefix}/lib64). Note that this leaves the default values untouched just as they were before (both default to 'lib') if the variables are not set.