Rather than testing that a constant expression produces so many
instructions, test that a variety of of such expressions produce the
same number of instructions. This will make future changes in the
compiler less likely to break this test.
Allow a continuation on a comment immediately after a shebang to make
this traditional hack possible:
#!/bin/sh
# this next line is ignored by jq \
exec jq -f "$0" "$@"
# jq code follows
But continue only on the first line following a shebang, and only if
it's a comment.
