linux-initrd: Silence Guile warnings.

Previously, since the switch to Guile 3, we'd see this warning repeated
several times at boot time:

  WARNING: …: imported module (guix build utils) overrides core binding `delete'

* gnu/system/linux-initrd.scm (raw-initrd): In gexp, #:hide 'delete'
from (guix build utils).  Wrap 'boot-system' in 'parameterize'.

vm: Use 'let-system'.

* gnu/system/vm.scm (expression->derivation-in-linux-vm)[check]: New macro.
[builder]: Use 'let-system' and 'check' instead of referencing
'%current-system' and '%current-target-system'.

utils: 'target-arm32?' & co. take an optional parameter.

* guix/utils.scm (target-arm32?, target-aarch64?)
(target-arm?, target-64bit?): Make 'target' an optional parameter.

gexp: Add 'let-system'.

* guix/gexp.scm (<system-binding>): New record type.
(let-system): New macro.
(system-binding-compiler): New procedure.
(default-expander): Add 'self-quoting?' case.
(self-quoting?): New procedure.
(lower-inputs): Add 'filterm'.  Pass the result of
'mapm/accumulate-builds' through FILTERM.
(gexp->sexp)[self-quoting?]: Remove.
* tests/gexp.scm ("let-system", "let-system, target")
("let-system, ungexp-native, target")
("let-system, nested"): New tests.
* doc/guix.texi (G-Expressions): Document it.

gexp: Compilers can now return lowerable objects.

* guix/gexp.scm (lower-object): Iterate if LOWERED is a struct.
(lower+expand-object): New procedure.
(gexp->sexp): Use it.
(define-gexp-compiler): Adjust docstring.

bootloader: grub: Refer to the native 'grub-mklayout' and font file.

* gnu/bootloader/grub.scm (eye-candy): Refer to the native FONT-FILE.
(keyboard-layout-file): Refer to the native 'grub-mklayout'.

gnu: python-libmpsse: Update to 1.4.1.

* gnu/packages/embedded.scm (python-libmpsse): Update to 1.4.1.
[arguments]<#:phases>[set-environment-up]:
Fix build with Python 3.8.

gnu: kicad: Re-use common fields in add-ons.

* gnu/packages/engineering.scm (kicad-i18n, kicad-symbols): Re-use
kicad's VERSION and HOME-PAGE.
(kicad-symbols, kicad-footprints, kicad-packages3d, kicad-templates):
Re-use kicad's VERSION.

gnu: kicad-templates: Update to 5.1.6.

* gnu/packages/engineering.scm (kicad-templates): Update to 5.1.6.

gnu: kicad-packages3d: Update to 5.1.6.

* gnu/packages/engineering.scm (kicad-packages3d): Update to 5.1.6.

gnu: kicad-footprints: Update to 5.1.6.

* gnu/packages/engineering.scm (kicad-footprints): Update to 5.1.6.

gnu: kicad-symbols: Update to 5.1.6.

* gnu/packages/engineering.scm (kicad-symbols): Update to 5.1.6.

gnu: kicad-i18n: Update to 5.1.6.

* gnu/packages/engineering.scm (kicad-i18n): Update to 5.1.6.

gnu: kicad: Update to 5.1.6.

* gnu/packages/engineering.scm (kicad): Update to 5.1.6.
[source]: Use GIT-FETCH & GIT-FILE-NAME.

gnu: kicad-i18l: Fix typo in… name.

* gnu/packages/engineering.scm (kicad-i18n): New old variable previously…
(kicad-i18l): …this.  Redefine using DEPRECATED-PACKAGE.
(kicad)[arguments, native-inputs]: Adjust accordingly.

gnu: oil-shell: Rename to "oil".

* gnu/packages/shells.scm (oil): Rename variable from…
(oil-shell): …this.  Redefine using DEPRECATED-PACKAGE.

Signed-off-by: Tobias Geerinckx-Rice <me@tobias.gr>

gnu: clamav: End snippet in truth.

* gnu/packages/antivirus.scm (clamav)[source]: Return #t from snippet.

gnu: clamav: Update to 0.102.3.

* gnu/packages/antivirus.scm (clamav): Update to 0.102.3.

gnu: ethtool: Update to 5.6.

* gnu/packages/networking.scm (ethtool): Update to 5.6.
[native-inputs]: Add pkg-config.
[inputs]: Add libmnl.

gnu: openconnect: Update to 8.10 [fixes CVE-2020-12823].

* gnu/packages/vpn.scm (openconnect): Update to 8.10.