`makeWrapper` and `wrapProgram` are being invoked on all kinds of
wacky things (usually with the help of bash globs or other machine
assistance).
So far, I have come across `wrapProgram` being invoked on a directory,
as well as on the empty string.
As far as I can tell, it's only valid to invoke these utilities on a
normal (non-directory, non-device) executable file. This commit
enforces that precondition.
Previously, makeWrapper would accept arguments it didn't recognize,
potentially allowing argument misspellings or broken callers.
Now, makeWrapper dies with a backtrace if it is called incorrectly.
Also changes `wrapProgram` so that it doesn't pass through the first
argument twice --- this was tripping up the argument checking.
extraFlagsArray should not be exposed outside of `makeWrapper`, it
should only be possible to set it inside a script supplied via the
`--run` argument.
The tests need to expand passed variable and very carefully.
I could see no other easy way than to change single-quoting in
makeWrapper to double-quoting.
The tests now fail with the same problem as on master...
By default `makeWrapper` will not set argv[0] (this is a reversion to
the old default behavior). Based on the breakage we have seen from
changing the default, this is what most people want. The `wrapProgram`
function will send `--argv0 '"$0"'` to `makeWrapper`, i.e. it will
continue to pass-through the argv[0] that the wrapper is called with.
