package/log4cxx: select boost chrono and date-time with gcc < 7

Fix the following build failure raised since commit
4e267a7d3d5d350710a81ada188a1629348e4b4a:

-- Found Boost: /home/buildroot/autobuild/instance-3/output-1/host/sh4-buildroot-linux-uclibc/sysroot/usr/include (found version "1.77.0") found components: thread chrono atomic missing components: date_time

Fixes:
 - http://autobuild.buildroot.org/results/e7443e3bc955e7eddd7bed63e2728880dabb31a7

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

package/log4cxx/Config.in

@@ -12,6 +12,8 @@ config BR2_PACKAGE_LOG4CXX
 	select BR2_PACKAGE_APR_UTIL
 	select BR2_PACKAGE_BOOST if !BR2_TOOLCHAIN_GCC_AT_LEAST_7
 	select BR2_PACKAGE_BOOST_ATOMIC if !BR2_TOOLCHAIN_GCC_AT_LEAST_7
+	select BR2_PACKAGE_BOOST_CHRONO if !BR2_TOOLCHAIN_GCC_AT_LEAST_7
+	select BR2_PACKAGE_BOOST_DATE_TIME if !BR2_TOOLCHAIN_GCC_AT_LEAST_7
 	select BR2_PACKAGE_BOOST_THREAD if !BR2_TOOLCHAIN_GCC_AT_LEAST_7
 	help
 	  Apache log4cxx is a logging framework for C++ patterned