We ship the mkosi files to make sure we can test our own code. A good
chunk of our code (and the main reason to use qemu rather than nspawn)
is the EFI code, i.e. in sd-boot and the EFI stub. Hence it's bad idea
to use qemu headless mode, since that means we bypass all that.
Let's hence toggle the defaults here, but keep the line in place, to
make it easy to switch back if someone wants the speed, rather than the
testing.
With this change, "mkosi build" will automatically build systemd for the
current distro without any further configuration. If people want to do a
cross-distro build by default, they can still create mkosi.default, but I
assume that this is relatively rare.
If people have symlinked mkosi.default to one of the files in .mkosi/, they'll
need to adjust the symlink.
(Building without configuration would always fail, since systemd has many many
required dependencies. I think it's nicer to do the most commonly expected
thing by default, i.e. rebuild for the current distro.)
Mkosi is nowadays packaged for most distros, so recommend installing of distro
packages as the primary installation mechanism.
- InstallDirectory caches the install part of the build process
which speeds up incremental builds a little and allows inspecting
the installed components in mkosi.installdir.
- SourceFileTransferFinal copies the source files to the final
image which makes the gdb experience in qemu/systemd-nspawn a bit
nicer as it can now find the source files and show the source code
in the gdb cli itself.
