system: vm: Use the image API to generate QEMU images.

Also add a volatile? argument to the virtual-machine record. When volatile? is
true generate a QEMU script that mounts an overlay on top of a read only
storage. When volatile? is false, use a persistent, read-write storage.

* gnu/system/vm.scm (common-qemu-options): Add a rw-image? argument to use a
persistent storage.
(system-qemu-image/shared-store-script): Add a volatile? argument and honor
it. Use the image API to build the QEMU image.
(<virtual-machine>)[volatile?]: New field.
(virtual-machine-compiler): Pass the volatile? argument to the
system-qemu-image/shared-store-script procedure.

system: image: Add docker support.

* gnu/system/image.scm (docker-image, docker-image-type): New variables.
(system-docker-image): New procedure.
(image->root-file-system): Add docker image support.
(system-image): Ditto.

image: Add a shared-network? field.

* gnu/image.scm (<image>)[shared-network?]: New field.

image: Add a shared-store? field.

* gnu/image.scm (<image>)[shared-store?]: New field.

build: image: Add optional closure copy support.

* gnu/build/image.scm (initialize-root-partition): Add a closure-copy?
argument and honor it.

gnu: pre-commit: Update to 2.16.0.

* gnu/packages/version-control.scm (pre-commit): Update to 2.16.0.

Signed-off-by: Leo Famulari <leo@famulari.name>

gnu: gsequencer: Update to 3.14.5.

* gnu/packages/music.scm (gsequencer): Update to 3.14.5.
[source]<origin>: Update url.

Signed-off-by: Leo Famulari <leo@famulari.name>

gnu: gsequencer: Build with libsoup 2.

* gnu/packages/music.scm (gsequencer)[native-inputs]: Use the new style.
[inputs]: Replace libsoup with libsoup-minimal-2 and webkitgtk with
webkitgtk-with-libsoup2. Use the new style.

Signed-off-by: Leo Famulari <leo@famulari.name>

gnu: gnome-commander: Update to 1.12.3.1.

* gnu/packages/gnome.scm (gnome-commander): Update to 1.12.3.1.

Signed-off-by: Leo Famulari <leo@famulari.name>

gnu: openexr: Update to 3.1.3.

* gnu/packages/graphics.scm (openexr): Update to 3.1.3.

Signed-off-by: Leo Famulari <leo@famulari.name>

gnu: libksba: Fix cross-compilation.

* gnu/packages/gnupg.scm (libksba)[native-inputs]: Remove.

gnu: qemu-minimal: Actually remove unnecessary native-inputs.

This is a follow-up to commit d64bd1254a015dfc999431dc65b6c5f210e8e334.

* gnu/packages/virtualization.scm (qemu-minimal)[native-inputs]: Filter static
outputs and remove "gettext-minimal" instead of "gettext".

gnu: seabios: Build vgabios targets.

* gnu/packages/firmware.scm (seabios)[arguments]: Add new phase to build
various vgabiosen.  While at it, create a "bios-256k.bin" as expected by
QEMU.

gnu: seabios: Encode version information in the binary.

...to make the build deterministic.

* gnu/packages/firmware.scm (seabios)[arguments]:  Create a ".version" file as
expected by the build system.  While at it, set EXTRAVERSION as recommended by
upstream.

gnu: seabios: Update to 1.15.0.

* gnu/packages/firmware.scm (seabios): Update to 1.15.0.
[arguments]: Remove trailing #t's.
[native-inputs]: Remove label.

gnu: gcl: Avoid referencing GCC from the top-level.

* gnu/packages/lisp.scm (gcl)[arguments]: Use SEARCH-INPUT-FILE instead of
referencing the GCC variable.

gnu: rsync: Remove 3.1.3.

* gnu/packages/rsync.scm (rsync-next): Remove variable.
(rsync): Update to 3.2.3.  While at it, remove input labels.

chromium-extension: Avoid another usage of the store-mapped /tmp.

* gnu/build/chromium-extension.scm (make-crx): Use a Chromium profile relative
to the build directory instead of /tmp.  While here, remove obsolete comment.

gnu: emacs-eldev: Adjust to changes in emacs-build-system.

* gnu/packages/emacs-xyz.scm (emacs-eldev)[install-eldev-executable]: Use
elpa-directory for ELDEV_LOCAL.

gnu: xorg-server: Update to 21.1.2 [security fixes].

Fixes CVE-2021-4008, CVE-2021-4009, CVE-2021-4010, and CVE-2021-4011.

* gnu/packages/xorg.scm (xorg-server): Update to 21.1.2.
(xorg-server-for-tests): Use version 21.1.1.