This makes the tests more reproducable. In particular it avoids hiding
a WARN_CREATE_GLOBAL error when the dev happens to have defined that
variable in the environment (cf. next commit).
Fixeszsh-users/zsh-syntax-highlighting#262.
Currently, 'make quiet-test' uses Perl. However, since it is considered a development
tool rather than a user-facing tool, users and downstream packages needn't install Perl.
Furthermore, even this dev-only dependency may be dropped in the future.
The only difference between tests/tap-filter here and the one in the issue is using
a `cat` subshell v. using 'undef $/; <STDIN>'.
Change quoting to only quote the shell variable, not the make variable. This
allows the leading '~' to be unescaped for make's sh to expand.
Followup to b1619c0013.
test failure would not be reflected by the exit code of 'make'.
Setting a shell parameter in the left-hand side of a pipe is not visible to
commands after the pipe, because the left-hand side forks. (That's true both
in 'sh' used by 'make' and in 'zsh' that runs tests/test-highlighting.zsh, at
least on my system.) Therefore, move the colorizing hook to where it doesn't
interfere with setting the $something_failed (in tests/test-highlighting.zsh)
and $result (in Makefile) parameters.
