-DNO_WARN_X86_INTRINSICS -mvsx flags are necessary on PPC64(LE), but
those flags haven't been added yet to libobs.pc, making some plugins
fail to build.
In 'libobs/CMakeLists.txt', use '${CMAKE_INSTALL_LIBDIR}' instead of
'${CMAKE_INSTALL_PREFIX}/lib', as the latter results into 'libobs.pc'
being installed under '/lib' when '/lib64' would be more appropriate.
In 'libobs/libobs.pc.in', use '@CMAKE_INSTALL_FULL_LIBDIR@' for
'libdir', '@CMAKE_INSTALL_FULL_INCLUDEDIR@' for 'includedir',
and '@CMAKE_INSTALL_PREFIX@' for 'prefix'.
Gentoo-Bug: https://bugs.gentoo.org/644538