Boost Build 1.59 errors when the site-config.jam is completely missing the "using boost" line

gistfile1.txt

When the site-config.jam has no "using boost" line at all:


c:\Work\github\TimSimpson\BoostBuildExamples\boost-test>b2 address-model=64 toolset=msvc-12.0 link=shared
Performing configuration checks

    - 32-bit                   : yes
    - arm                      : no
    - mips1                    : no
    - power                    : no
    - sparc                    : no
    - x86                      : yes
    - symlinks supported       : no
    - junctions supported      : yes
    - hardlinks supported      : yes
C:/Tools/Local/boost/boost_1_59_0/tools/build/src/build\generators.jam:1102: in ensure-type from module generators
error: target { link%link.do-link-recursively-chrono/stopwatches-headers. { libs/chrono/stopwatches/include/boost. }
} has no type
C:/Tools/Local/boost/boost_1_59_0/tools/build/src/build\generators.jam:1359: in generators.construct from module gene
rators
C:/Tools/Local/boost/boost_1_59_0/tools/build/src/build\targets.jam:1553: in construct from module object(typed-targe
t)@141
C:/Tools/Local/boost/boost_1_59_0/tools/build/src/build\targets.jam:1353: in class@basic-target.generate from module
object(typed-target)@141
C:/Tools/Local/boost/boost_1_59_0/tools/build/src/build\targets.jam:774: in generate-really from module object(main-t
arget)@1709
C:/Tools/Local/boost/boost_1_59_0/tools/build/src/build\targets.jam:746: in class@main-target.generate from module ob
ject(main-target)@1709
C:/Tools/Local/boost/boost_1_59_0/tools/build/src/build\targets.jam:272: in class@project-target.generate from module
 object(project-target)@107
C:/Tools/Local/boost/boost_1_59_0/tools/build/src\build-system.jam:707: in load from module build-system
C:\Tools\Local\boost\boost_1_59_0\tools\build\src/kernel\modules.jam:295: in import from module modules
C:\Tools\Local\boost\boost_1_59_0\tools\build\src/kernel/bootstrap.jam:139: in boost-build from module
C:\Tools\Local\boost\boost_1_59_0\boost-build.jam:17: in module scope from module

Sorry for silly question, but what exactly does one put into a "using boost" line? I've spent a while Googling that phrase but have turned up only English instances rather than Boost.Build syntax.