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.

.gitmodules

@@ -2,6 +2,9 @@
 	path = submodules/buildroot
 	url = https://github.com/cirosantilli/buildroot
 	ignore = dirty
+[submodule "submodules/crosstool-ng"]
+	path = submodules/crosstool-ng
+	url = https://github.com/crosstool-ng/crosstool-ng
 [submodule "submodules/gem5"]
 	path = submodules/gem5
 	url = https://gem5.googlesource.com/public/gem5