Lower msvc build verbosity level

Hello,

could we perhaps lower the verbosity level of the msvc build (in
src/tools/msvc/build.pl) from "detailed" to "normal"? In my experiment,
this reduces the size of the build log by 96.4 percent (from 12.5 MiB to
438 KiB), or if the log is not redirected, it shortens the build time by
45 percent, from just under 6 minutes to 3.

The lines that would not be logged anymore are mostly "Task [or Target]
so-and-so skipped, due to false condition". All the compiler, linker,
etc. command lines are still there.

Also, with the "detailed" logs, loading the buildfarm status page for a
failure in the Make stage is really painful.

--
Christian