ntp: fix missing optional dependencies

ntpq and ntpdc may depends on libedit and libcap.

$ arm-linux-readelf -d ./usr/bin/ntpdc | grep NEEDED
 0x00000001 (NEEDED)                     Shared library: [libcap.so.2]
 0x00000001 (NEEDED)                     Shared library: [libm.so.6]
 0x00000001 (NEEDED)                     Shared library: [libedit.so.0]
 0x00000001 (NEEDED)                     Shared library: [libncursesw.so.6]
 0x00000001 (NEEDED)                     Shared library: [libssl.so.1.0.0]
 0x00000001 (NEEDED)                     Shared library: [libcrypto.so.1.0.0]
 0x00000001 (NEEDED)                     Shared library: [libpthread.so.0]
 0x00000001 (NEEDED)                     Shared library: [libc.so.6]

However, build order with these libraries is not defined.

In order to keep things simple, we enforce build order even if ntpq/ntpdc are
not selected.

Signed-off-by: Jérôme Pouiller <jezz@sysmic.org>
[Thomas: use --without-lineeditlibs.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>