l4: bootstrap_custom: Tell bootstrap memory layout by passing through cmdline.

diff --git a/l4 b/l4
index 5ebb28e721042d0ceecd76e4cdccab4b9396dcc5..8abb6a185f8761b6928b3f183d384e842878de99 160000 (submodule)
--- a/l4
+++ b/l4
@@ -1 +1 @@
-Subproject commit 5ebb28e721042d0ceecd76e4cdccab4b9396dcc5
+Subproject commit 8abb6a185f8761b6928b3f183d384e842878de99