Fixed usage of the exec-maven-plugin to use same JDK as was used to run Maven

[dmatej]

• Noticed when reviewing https://github.com/jakartaee/platform-tck/pull/1291
• If you use Ant exec somewhere - that is the same situation.
• Critical especially when you use .mavenrc to configure Maven but your local system uses older java.

CC @alwin-joseph @anajosep @arjantijms @cesarhernandezgt @dblevins @m0mus @edbratt @gurunrao @jansupol @jgallimore @kazumura @kwsutter @LanceAndersen @bhatpmk @RohitKumarJain @shighbar @gthoman @brideck @OndroMih @dmatej @starksm64 @scottmarlow

[scottmarlow]

Thanks @dmatej!