FunctionalJavascript tests are skipped in test-only change when concurrent=0

Migrated issue

Reported by: jonathan1055

Related to !355 (merged)

Problem/Motivation

The "test-only changes" job does not properly run javascript tests when using the plain phpunit binary (_PHPUNIT_CONCURRENT=0). The modified test is attempted but is skipped, as in this example

The log shows

SSSSSSSS                                                            8 / 8 (100%)
Time: 01:12.995, Memory: 6.00 MB
OK, but some tests were skipped!
Tests: 8, Assertions: 0, Skipped: 8.

There is no problem when using run-tests.sh (_PHPUNIT_CONCURRENT=1)

Proposed resolution

Remaining tasks

Related issue: Issue #3523139