feat: vmtest.sh: the boot loader test for every loader the ISO advertises

One VM per loader, Steam Machine (--fremont): Steamify's state as its menu sees it,
OS name untouched, loader identity, the DKMS modules for every kernel, Steamify's
loader-specific code (hdmi_remove_boot_param), a kernel update, and a reboot into
each of the two kernels. Headless by default with a log Konsole (--window shows
the VMs). Fails when an advertised loader has no test. Limine 41, systemd-boot 40,
GRUB 40 checks pass.

share/bootloader-test/kernel-update.sh

@@ -0,0 +1,28 @@
+#!/bin/bash
+# Guest side: reinstall both kernels + headers (what an update does: the
+# DKMS hook rebuilds the modules, mkinitcpio and the boot loader's hook run).
+pass() { echo "PASS $*"; }; fail() { echo "FAIL $*"; }
+start=$(date +%s)
+sudo pacman -S --noconfirm linux-cachyos linux-cachyos-lts linux-cachyos-headers linux-cachyos-lts-headers > /tmp/kernel-update.log 2>&1
+rc=$?
+sed 's/\x1b\[[0-9;]*m//g' /tmp/kernel-update.log | grep -E "^==> dkms|Building image|Generating grub|sdboot|limine|error" | cut -c1-140
+[[ $rc -eq 0 ]] && pass "pacman kernel reinstall exit 0" || fail "pacman exit $rc"
+for k in $(ls /usr/lib/modules); do
+    for m in cros-ec-cec leds-valve steamify-fremont-poweroff; do
+        compgen -G "/usr/lib/modules/$k/updates/dkms/$m.ko*" >/dev/null || fail "$m not rebuilt for $k"
+    done
+done
+[[ $(dkms status | grep -c ': installed') -eq $((3 * $(ls /usr/lib/modules | wc -w))) ]] && pass "DKMS rebuilt 3 modules for each kernel" || fail "DKMS status after the update"
+# The images: /boot/initramfs-*.img (GRUB, systemd-boot); Limine keeps them per kernel
+# under /boot/<machine-id>/<kernel>/initramfs (limine-mkinitcpio) and rewrites limine.conf.
+if [[ "$LOADER" == limine ]]; then
+    # limine-entry-tool copies an image only when its content changed (same version = untouched):
+    # the hook ran when both images were built and limine.conf was regenerated.
+    n=$(sed 's/\x1b\[[0-9;]*m//g' /tmp/kernel-update.log | grep -c 'Creating zstd-compressed initcpio image')
+    [[ $n -ge 2 ]] && pass "Limine's hook built the initramfs for both kernels" || fail "Limine's hook built $n initramfs image(s)"
+    [[ $(sudo stat -c %Y /boot/limine.conf) -ge $start ]] && pass "limine.conf regenerated" || fail "limine.conf not regenerated"
+else
+    for img in /boot/initramfs-linux-cachyos.img /boot/initramfs-linux-cachyos-lts.img; do
+        [[ $(sudo stat -c %Y "$img") -ge $start ]] && pass "$(basename "$img") rebuilt" || fail "$(basename "$img") not rebuilt"
+    done
+fi