runtime-link=static link=shared does nothing

boost version: `1.72.0`

I want to build boost dlls with static runtime to link into an executable with another dll with static runtime. Another dll is a protobuf dll which I have to link with static runtime to resolve some issue around a static data constructor which internally accessing protobuf globals.

The output:
```
...found 1 target...

The Boost C++ Libraries were successfully built!

The following directory should be added to compiler include paths:

D:\_3dparty\vc2017_x86\utility\boost\boost-1_72_0-release

The following directory should be added to linker library paths:

D:\_3dparty\vc2017_x86\utility\boost\boost-1_72_0-release\stage\lib
```

But nothing else happens.