chore(build): do not set CMAKE_INSTALL_LIBDIR and never with _libdir!

4 jobs for <span class="ref-name">fix/rpm-install-libdir</span> in 25 minutes and 22 seconds (queued for 2 minutes and 26 seconds)
Status Job ID Name Coverage
  Test
passed #7265
docker
job-debian9-ninja-clang

00:06:05

passed #7264
docker
job-debian9-ninja-gcc

00:07:22

passed #7266
macosx
job-macosx-ninja

00:08:53

passed #7267
windows
job-windows-vs2015

00:11:54