* gnu/tests/install.scm (%simple-installation-script): New variable.
Contains installation script formerly in 'run-install'.
(run-install): Add 'target-os', 'target-os-source', and #:script
parameters. Honor them.
(qemu-command/writable-image): New procedure.
(%test-installed-os): Use it.
This is a followup to 037f9e07cd.
Reported by Mark H Weaver.
* gnu/tests/install.scm (%minimal-os): Pass a <marionette-configuration>
object as the value for the MARIONETTE-SERVICE-TYPE.
* gnu/tests.scm (<system-test>): New record type.
(write-system-test, test-modules, fold-system-tests)
(all-system-tests): New procedures.
* gnu/tests/base.scm (%test-basic-os): Turn into a <system-test>.
* gnu/tests/install.scm (%test-installed-os): Likewise.
* build-aux/run-system-tests.scm (%system-tests): Remove.
(run-system-tests): Use 'all-system-tests'.