MTAF has runtests.sh script which allow to do that. You can pass parameters to the script in case you would like to run several configurations or browsers at the same time. For passing parameters use next template:
runtests.sh application:browser, application:browser
Where application is name of link to default application (by default: *mage).
You need command like this:
/path/to/script/runtests.sh mage:googlechrome, mage:firefox
And use it as value in phpunit in Jenkins configuration. Now you have something like this:
<target name="phpunit" description="Run unit tests with PHPUnit">
<exec command="phpunit --configuration=${basedir}/tests/phpunit.xml
--log-junit ${basedir}/build/logs/junit.xml
--coverage-clover ${basedir}/build/logs/clover.xml
--coverage-html ${basedir}/build/coverage"/>
</target>
Change to command provided above and it should do the trick.
And last, if you want to keep all this phpunit arguments, open file runtests.sh, find function runTest() and change line
eval exec "/usr/bin/phpunit -c ${phpunitArr[${i}]}/phpunit.xml &"
to line with your phpunit arguments:
eval exec "/usr/bin/phpunit -c ${phpunitArr[${i}]}/phpunit.xml --log-junit /path/to/build/logs/junit.xml --coverage-clover /path/to/build/logs/clover.xml &"