scripts: execute each steps in a subshell

To avoid variable leakage from one step to another, isolate the
steps from each others by running them in their own sub-shell.

This avoids variables leaking from one step to the others.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

scripts/crosstool-NG.sh.in

@@ -578,7 +578,7 @@ if [ "${CT_ONLY_DOWNLOAD}" != "y" -a "${CT_ONLY_EXTRACT}" != "y" ]; then
             fi
         fi
         if [ ${do_it} -eq 1 ]; then
-            do_${step}
+            ( do_${step} )
             if [ "${CT_STOP}" = "${step}" ]; then
                 do_stop=1
             fi