* gnu/bootloader/grub.scm (grub-configuration-file): Add support for
chain-loader.

Signed-off-by: Julien Lepiller <julien@lepiller.eu>

In some specific cases where the device tree file is already loaded in RAM, it
can be preferable that the bootloader does not try to use a device tree from
the Linux kernel tree.

* gnu/bootloader.scm (<bootloader-configuration>)[device-tree-support?]: New field.
* gnu/bootloader/extlinux.scm (extlinux-configuration-file): Add FDTDIR line
based on <device-tree-support?> field of <bootloader-configuration>.
* doc/guix.texi (Bootloader Configuration)[device-tree-support?]: Add
documentation for the new field.

* gnu/bootloader/grub.scm (grub-efi32-bootloader): New variable.
(install-grub-efi32): New variable.
* gnu/build/bootloader.scm (install-efi): Add a 'targets' keyword
argument.
(install-efi-loader): Likewise.
* gnu/build/image.scm (initialize-efi32-partition): New procedure.
* gnu/packages/bootloaders.scm (grub-efi32): New variable.
* gnu/system/image.scm (esp32-partition): New variable
(efi32-disk-image): New variable.
(efi32-raw-image-type): New variable.
(system-disk-image)[partition-image]: Set '#:grub-efi32' when
calling the partition initializer.

Signed-off-by: Mathieu Othacehe <othacehe@gnu.org>

For single-disk installs (external USBs) and for amnesiac UEFIs, Guix is not
found using its default Grub EFI bootloader location of
/boot/efi/EFI/Guix/grubx64.efi means the Guix install will not be found.

To handle this, we can place the bootloader file in the UEFI specification
location, overwriting any other OS that may have placed a file there. This
location is namely /boot/efi/EFI/BOOT/BOOTX64.efi. Grub has explicit support
for this location/situation with the `--removable` flag.

* gnu/bootloader/grub.scm (install-grub-efi-removable)
(grub-efi-removable-bootloader): New variables.
* doc/guix.texi (Bootloader Configuration): Document it.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

* gnu/bootloader/grub.scm (grub-setup-io): Fix serial mode display by
declaring the serial property before the terminal_input and terminal_output
properties.

* gnu/bootloader/grub.scm (grub-configuration-file): Add 'insmod
luks2'.
* gnu/system/mapped-devices.scm (open-luks-device): Create
'/run/cryptsetup/' directory.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

The old 'target' field is deprecated; adjust the sources to use the new
'targets' one instead.

* doc/guix-cookbook.texi<target>: Replace by 'targets'.
* gnu/bootloader/grub.scm: Likewise.
* gnu/installer/parted.scm: Likewise.
* gnu/machine/digital-ocean.scm: Likewise.
* gnu/system/examples/asus-c201.tmpl: Likewise
* gnu/system/examples/bare-bones.tmpl: Likewise
* gnu/system/examples/bare-hurd.tmpl: Likewise
* gnu/system/examples/beaglebone-black.tmpl: Likewise
* gnu/system/examples/desktop.tmpl: Likewise
* gnu/system/examples/docker-image.tmpl: Likewise
* gnu/system/examples/lightweight-desktop.tmpl: Likewise
* gnu/system/examples/vm-image.tmpl: Likewise
* gnu/system/examples/yggdrasil.tmpl: Likewise
* gnu/system/hurd.scm: Likewise
* gnu/system/images/hurd.scm: Likewise
* gnu/system/images/novena.scm: Likewise
* gnu/system/images/pine64.scm: Likewise
* gnu/system/images/pinebook-pro.scm: Likewise
* gnu/system/images/rock64.scm: Likewise
* gnu/system/install.scm: Likewise
* gnu/system/vm.scm: Likewise
* gnu/tests.scm: Likewise
* gnu/tests/ganeti.scm: Likewise
* gnu/tests/install.scm: Likewise
* gnu/tests/nfs.scm: Likewise
* gnu/tests/telephony.scm: Likewise
* tests/boot-parameters.scm: Likewise
* tests/system.scm: Likewise

This fixes boot breakage introduced in commit:

  a65c935e29766940148d52b8116634b1e1cbcba6

Multiple files were still needed, but the filenames changed.

* gnu/bootloader/u-boot.scm (install-allwinner64-u-boot): Update to
  use both SPL and u-boot files with new filenames.

* gnu/bootloader/grub.scm (install-grub-efi-netboot): Fix typo.

* gnu/bootloader/u-boot.scm (install-allwinner64-u-boot): Update to
  use a single file to install.