Windows bootstrap fixes needed for the CI and other things

commit 74f3581c:

cerbero/bootstrap: Fix git autocrlf message on Windows
Specify that it should be run inside the MSYS shell, and that the
global config must be changed, not the config inside the cerbero git
repository.

commit 6a4953bc:

cerbero/wipe: Don't wipe build tools sources if --keep-sources

commit 4d75f4fc:

cerbero/build-tools: Transfer vs_install_* settings to build tools
Otherwise custom vs install locations passed via `-c` to cerbero
aren't set on the build tools config. In practice, this leads to .lib
files not being generated. In theory, this also causes build tools
recipes to not be buildable with Visual Studio, which might be
a problem in the future.

commit 599a6cd7:

cerbero/windows: Don't require visual studio for genlib
We don't actually require Visual Studio if you don't enable the
variant.