boost: test needs system and timer

output/host/usr/bin/m68k-linux-readelf -d output/staging/usr/lib/libboost_prg_exec_monitor.so

Dynamic section at offset 0xdef8 contains 29 entries:
  Tag        Type                         Name/Value
 0x00000001 (NEEDED)                     Shared library: [libboost_timer.so.1.67.0]
 0x00000001 (NEEDED)                     Shared library: [libboost_system.so.1.67.0]

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/boost/Config.in

@@ -289,6 +289,8 @@ config BR2_PACKAGE_BOOST_SYSTEM
 config BR2_PACKAGE_BOOST_TEST
 	bool "boost-test"
 	depends on BR2_USE_MMU # fork()
+	select BR2_PACKAGE_BOOST_SYSTEM
+	select BR2_PACKAGE_BOOST_TIMER
 	help
 	  Support for simple program testing, full unit testing, and for
 	  program execution monitoring.