Cleanup Bash scripts.

This makes them pass shellcheck. Except for a few unused
export warnings.

I also wonder if the majority of these files should be
in the root of the project, or should be moved to "build-scripts"
(or should still even exist).

a few minor changes

one more minor changes

env-gcc-4.8-rpi.sh

@@ -1,14 +1,14 @@
 #!/usr/bin/env bash
 #
 # Look for GCC-4.8
-x=`which gcc-4.8`
-gdir=`dirname $x`
+x=$(which gcc-4.8)
+gdir=$(dirname "${x}")
 
-export CC="$gdir/gcc-4.8"
-export CPP="$gdir/cpp-4.8"
-export CXX="$gdir/g++-4.8"
+CC="${gdir}/gcc-4.8"
+CPP="${gdir}/cpp-4.8"
+CXX="${gdir}/g++-4.8"
+export CC CPP CXX
 
-echo Starting subshell. Type exit to exit.
-
-$SHELL
+echo "Starting subshell. Type exit to exit."
 
+${SHELL}