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.

build-all

@@ -15,8 +15,14 @@ done
 shift "$(($OPTIND - 1))"
 for arch in $archs; do
   ./build-qemu --arch "$arch"
-  ./build-buildroot --arch "$arch" --gem5 --kernel-modules -l "$@"
   if "$gem5"; then
     ./build-gem5 --arch "$arch"
   fi
+  ./build-buildroot --arch "$arch" --gem5 --kernel-modules -l "$@"
+  if [ ! "$arch" = x86_64 ]; then
+    ./build-crosstool-ng --arch "$arch"
+    ./build-baremetal --arch "$arch"
+    ./build-baremetal --arch "$arch" -g
+    ./build-baremetal --arch "$arch" -g --machine RealViewPBX
+  fi
 done