Debian: enable multiarch

Use /usr/lib/x86_64-linux-gnu/ instead of /usr/lib.
https://wiki.debian.org/Multiarch

A prerequisite for proper #1085 fix

debian/rules

@@ -15,7 +15,6 @@ DEB_CMAKE_NORMAL_ARGS := -DCMAKE_INSTALL_PREFIX="$(DEB_CMAKE_INSTALL_PREFIX)" \
 	-DCMAKE_VERBOSE_MAKEFILE=ON \
 	-DCMAKE_INSTALL_SYSCONFDIR=/etc \
 	-DCMAKE_INSTALL_LOCALSTATEDIR=/var \
-	-DCMAKE_INSTALL_LIBDIR=/usr/lib \
 	-DENABLE_BUNDLED_LIBYAML=OFF \
 	-DENABLE_DIST=ON
 #     -DCMAKE_C_FLAGS="$(CFLAGS)" \

debian/tarantool-common.dirs

 /etc/tarantool/instances.available
 /etc/tarantool/instances.enabled
-/usr/lib/tarantool
 /var/log/tarantool
 /var/lib/tarantool