This reverts commit fc232422201c0364dbd57826c9a137cc1239caea, reversing
changes made to 754816b84b98afdc0727e13dd66e1698b097de6a.
We don't have many binaries yet. Comment on the original merge commit.
Before the code would fail silently for zero values and with some output for
empties. We now currently handle both via defaulting value to zero and making
`let` return success error code when there's no syntax error.
Now is an opportune time to do this, as the infixSalt conversion in
`add-flags.sh` ensures that all the relevant `NIX_*` vars will be
defined even if empty.
This makes the response file handling more consistent with GCC.
For example, a reponse file may contain:
"-Wl,$ORIGIN"
GCC will treat this as a double quoted string and not expand the
variable reference. Previously, cc-wrapper would expand the variable
in the same was as if the string was provided on the command line.
