torture: Make TORTURE_TRUST_MAKE available in kvm-again.sh environment

Because the TORTURE_TRUST_MAKE environment variable is not recorded,
kvm-again.sh runs can result in the parse-build.sh script emitting
false-positive "BUG: TREE03 no build" messages.  These messages are
intended to complain about any lack of compiler invocations when the
--trust-make flag is not given to kvm.sh.  However, when this flag is
given to kvm.sh (and thus when TORTURE_TRUST_MAKE=y), lack of compiler
invocations is expected behavior when rebuilding from identical source
code.

This commit therefore makes kvm-test-1-run.sh record the value of the
TORTURE_TRUST_MAKE environment variable as an additional comment in the
qemu-cmd file, and also makes kvm-again.sh reconstitute that variable
from that comment.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>