RFR: Fix jtreg test java/lang/ProcessBuilder/Basic.java

[Siebenborn, Axel]

Hi,

I'm currently looking into jtreg failures,  that occur with the portola jdk. 

A first issue I tackled, was the failing test 'java/lang/ProcessBuilder/Basic.java'

The test copies the executable '/bin/true' and '/bin/false'. However, on alpine linux, these are just links to /bin/busybox.
Copying the busbox executable into a file with a different name won't result in the expected return codes. 

Another problem with this test is a bug in musl, that probably won't be fixed [1]. 'execvp' has not the fallback to /bin/sh.

Regards,
Axel

[1] http://www.openwall.com/lists/musl/2018/03/09/2