Don't add library dir suffix where we can expect it to already be present

INSTALL_LIBRARY_DIR should already handle the 64 suffeix. So there is no
need to additionally add it. This would lead to lib6464 otherwise.

Change-Id: Ibfc4fd3e5cad20c30a3677fe3ef482158af5f913
Signed-off-by: Justin Lecher <jlec@gentoo.org>
Merge topic '6464' into master

ffa7dc41 Don't add library dir suffix where we can expect it to already be present