package/ntpsec: new package

- set 'CC="$(HOSTCC)"' to avoid cross-compile failure (see [1]):

  /bin/sh: line 1: .../build/ntpsec-1_2_0/build/host/ntpd/keyword-gen: cannot execute binary file: Exec format error

  Waf: Leaving directory `.../build/ntpsec-1_2_0/build/host'
  Build failed
   -> task in 'ntp_keyword.h' failed with exit status 126 (run with -v to display more information)

- set '-std=gnu99"' to avoid compile failure with old compilers

- explicitly set PYTHON_CONFIG

- add patch 001-ntptime-fix-jfmt5-ofmt5-jfmt6-ofmt6-related-compile-.patch to
  fix ntptime jfmt5/ofmt5 jfmt6/ofmt6 related compile failure

- add patch 0002-wscript-remove-checks-for-bsd-string.h-fixes-host-co.patch to
  fix host-compile failure in case target libbsd is detected

- add SYSV init file (S49ntp)

- add example ntpd.conf (with legacy option enabled and provide skeleton
  for NTS configuration)

- add config option for NTS support

- add ntp user/group and run ntpd as restricted user

- add libcap dependency (compile time optional but needed for droproot
  support)

[1] https://gitlab.com/NTPsec/ntpsec/-/issues/694



Signed-off-by: Peter Seiderer <ps.report@gmx.net>
[Thomas: S49ntp -> S49ntpd]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>