gem5: update to 7bfb7f3a43f382eb49853f47b140bfd6caad0fb8

The update is required to include 3c3ca64b5f0dd9eef7b1ce1c65cc6e8e9147dd38
otherwise baremetal does not on VExpress.

baremetal: create a baremetal setup with crosstool-ng

buildroot: improve directory location: move out/dl inside
out/buildroot/download, and add a new out/buildroot/build level

tagline: generalize, deliver more value than howto, since now howtos
are starting to multiply

rename all top scripts to separate words with hyphen more consistently,
e.g. run-gdb instead of rungdb

getvar: list all variables

gem5: make m5out section to focus all releated information at

Prevent m5term Text file busy when rebuilding gem5 while it is running.

rootfs-post-build-script

@@ -0,0 +1,22 @@
+#!/usr/bin/env bash
+# This is run as part of:
+#      make target-finalize
+# which gets called by the default target.
+target_dir="$1"
+mkdir -p \
+  "${target_dir}/mnt/9p" \
+  "${target_dir}/mnt/out" \
+;
+# Maybe there is a cleaner way to get rid of those files,
+# like disabling some Buildroot packages, but no patience.
+#
+# As of 2d5f95b1839986ca6d7b568296374a2403d2693d
+# xorg must be removed or else we get a black screen:
+# https://bugs.busybox.net/show_bug.cgi?id=11066
+rm -rf \
+  "${target_dir}/etc/init.d/S01logging" \
+  "${target_dir}/etc/init.d/S20urandom" \
+  "${target_dir}/etc/init.d/S40network" \
+  "${target_dir}/etc/init.d/S40xorg" \
+  "${target_dir}/etc/init.d/S50sshd" \
+;