Allows to 'meson install --tags systemd-boot --no-rebuild' to install only the EFI
binaries, skipping the rest, for a very quick build:
$ ninja src/boot/efi/linuxx64.efi.stub
[21/21] Generating src/boot/efi/linuxx64.efi.stub with a custom command
$ ninja src/boot/efi/systemd-bootx64.efi
[10/10] Generating src/boot/efi/systemd-bootx64.efi with a custom command
$ DESTDIR=/tmp/foo meson install --tags systemd-boot --no-rebuild
Installing src/boot/efi/systemd-bootx64.efi to /tmp/foo/usr/lib/systemd/boot/efi
Requires Meson 0.60 to be used, prints a warning for unknown keyword
in earlier versions, but there's no failure
https://mesonbuild.com/Installing.html#installation-tags