fix: NVIDIA fix on Limine edits the existing cmdline line; early modules only when every kernel has them

Found by running it in a VM: the appended += line became literal text on the
kernel command line, and a kernel without the modules made limine-mkinitcpio
skip its boot entry.

tests/nvidia-test.sh

@@ -19,6 +19,8 @@ echo 0x8086 > "$T/drm/card0/device/vendor"; echo 0x030000 > "$T/drm/card0/device
 echo 0x10de > "$T/drm/card1/device/vendor"; echo 0x030000 > "$T/drm/card1/device/class"
 echo 0x2c02 > "$T/drm/card1/device/device"
 NVIDIA_DRM_DIR="$T/drm"
+mkdir -p "$T/mods/6.1.0-cachyos/kernel"; : > "$T/mods/6.1.0-cachyos/kernel/nvidia-drm.ko.zst"
+NVIDIA_MODULES_DIR="$T/mods"
 
 FAKE_DRIVER=1; check "finds the NVIDIA card as card1 beside an iGPU" nvidia_present
 FAKE_DRIVER=0; check "skips when the driver isn't installed" '! nvidia_present'
@@ -43,6 +45,11 @@ for loader in limine sdboot grub; do
     check "$loader: disable restores the file and drops the drop-in" '[[ "$(cat "$F")" == "$ORIG" && ! -f "$NVIDIA_INITRAMFS_CONF" ]]'
 done
 
+# A second kernel without the NVIDIA modules: no early-load drop-in, parameters still set.
+mkdir -p "$T/mods/6.6.0-lts/kernel"; F="$T/sdboot-manage.conf"; printf 'LINUX_OPTIONS="quiet"\n' > "$F"
+nvidia_boot_file() { echo "$F"; }; rm -f "$NVIDIA_INITRAMFS_CONF"; REBUILDS=0; nvidia_enable
+check "kernel without nvidia modules: no drop-in, parameters set" '[[ ! -f "$NVIDIA_INITRAMFS_CONF" ]] && grep -q "nvidia-drm.fbdev=1" "$F"'
+rm -rf "$T/mods/6.6.0-lts"
 FAKE_DRIVER=0; printf 'LINUX_OPTIONS="quiet"\n' > "$T/sdboot"; F="$T/sdboot"; REBUILDS=0; nvidia_enable
 check "no NVIDIA driver: nothing touched" '[[ "$(cat "$F")" == "LINUX_OPTIONS=\"quiet\"" && $REBUILDS == 0 ]]'
 exit $fail