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>

reporter_name="Antony Pavlov"

reporter_url=""

reporter_comment="Experimental toolchain for MIPS32r2"