Add a shortcute for /eval.sh

Create /eval_base64.sh to overcome quoting and newline limitations.

Documente poweroff's failure on readme.

rootfs_overlay/eval.sh

@@ -1,2 +1,18 @@
 #!/bin/sh
+echo "$lkmc_eval"
 eval "$lkmc_eval"
+
+# Ideally, this script would do just:
+#
+## Get rid of the '-'.
+#shift
+#echo "$@"
+#
+# However, the kernel CLI parsing is crap, and the 4.14 docs lie.
+#
+# In particular, not all that is passed after "-" goes to an argument to init,
+# e.g. stuff with dots like "- /poweroff.out" still gets treated specially and
+# does not go to init.
+#
+# This also likely means that the above solution is also unreliable in some cases,
+# and that in the end you just have to add a script to the root filesystem.

rootfs_overlay/eval_base64.sh

@@ -0,0 +1,2 @@
+#!/bin/sh
+eval "$(printf "$lkmc_eval" | base64 -d)"