build: install -- Add BINDIR var

Will need it for uninstall action.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Reviewed-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

Makefile.install

@@ -2,6 +2,7 @@
 # Installation paths.
 DESTDIR		?= /
 PREFIX		?= /usr/local
+BINDIR		?= $(PREFIX)/bin
 SBINDIR		?= $(PREFIX)/sbin
 MANDIR		?= $(PREFIX)/share/man
 SYSTEMDUNITDIR	?= $(PREFIX)/lib/systemd/system/
@@ -22,7 +23,7 @@ else
         endif
 endif
 
-export SBINDIR MANDIR SYSTEMDUNITDIR LOGROTATEDIR
+export BINDIR SBINDIR MANDIR SYSTEMDUNITDIR LOGROTATEDIR
 export INCLUDEDIR LIBDIR DESTDIR PREFIX
 
 install-tree: