[php-src] Issue #7991: Test Zend/tests/concat_003.phpt fails on slow machine

Issue: https://github.com/php/php-src/issues/7991 Comment Author: cmb69 That test is to ensure that concatenating lots of small allocations is not *too* slow. Catering to occassionally used *very* slow machines can easily hide real performance regressions. On AppVeyor CI, the test takes about 0.33 seconds; not sure about the performance on other CI, but obviously also less than a second. Like @damianwadley said, set SKIP_PERF_SENSITIVE, don't run the test at all, or patch it for your system.