boost: add selects for log

boost: add selects for log

log needs atomic, chrono, thread, date_time, filesystem, system and
regex

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

Dynamic section at offset 0xb9ed0 contains 34 entries:
  Tag        Type                         Name/Value
 0x00000001 (NEEDED)                     Shared library: [libboost_atomic.so.1.67.0]
 0x00000001 (NEEDED)                     Shared library: [libboost_chrono.so.1.67.0]
 0x00000001 (NEEDED)                     Shared library: [libboost_thread.so.1.67.0]
 0x00000001 (NEEDED)                     Shared library: [libboost_date_time.so.1.67.0]
 0x00000001 (NEEDED)                     Shared library: [libboost_filesystem.so.1.67.0]
 0x00000001 (NEEDED)                     Shared library: [libboost_system.so.1.67.0]
 0x00000001 (NEEDED)                     Shared library: [libboost_regex.so.1.67.0]

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