When openwrt toolchain uses eglibc (2.15) instead of uclibc,

When openwrt toolchain uses eglibc (2.15) instead of uclibc,
samba36-server build causes following error:

Package samba36-{client,server} is missing dependencies for the following
libraries:
librt.so.1

Fix is to define
DEPENDS:=+USE_EGLIBC:librt
which adds the librt dependency only if the eglibc is used by toolchain.
Patch tested by building the samba36 both with the the eglibc and uclibc
openwrt toolchains.

Signed-off-by: Mika Laitio <mika.laitio@nokia.com>
git-svn-id: svn://svn.openwrt.org/openwrt/packages@33010 3c298f89-4303-0410-b956-a3cf2f4a3e73