boost: type_erasure needs chrono, system, thread

output/host/usr/bin/arm-buildroot-linux-uclibcgnueabihf-readelf -d output/staging/usr/lib/libboost_type_erasure.so

Dynamic section at offset 0xcef0 contains 30 entries:
  Tag        Type                         Name/Value
 0x00000001 (NEEDED)                     Shared library: [libboost_thread.so.1.67.0]
 0x00000001 (NEEDED)                     Shared library: [libboost_chrono.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

@@ -323,6 +323,9 @@ config BR2_PACKAGE_BOOST_TIMER
 
 config BR2_PACKAGE_BOOST_TYPE_ERASURE
 	bool "boost-type_erasure"
+	select BR2_PACKAGE_BOOST_CHRONO
+	select BR2_PACKAGE_BOOST_SYSTEM
+	select BR2_PACKAGE_BOOST_THREAD
 	help
 	  Runtime polymorphism based on concepts.