[11u] RFR: 8240073: Fix 'test-make' build target in 11u

[Volker Simonis]

Hi,

can I please have a review for the following tiny change which fixes
the 'test-make' build target in 11u:

http://cr.openjdk.java.net/~simonis/webrevs/2020/8240073/
https://bugs.openjdk.java.net/browse/JDK-8240073

This is a tiny fix for a problem introduced by JDK-8212028 (which has
already been downported to 11u) and fixed in jdk 12 as part of
JDK-8210958 (which hasn't been downported yet and probably won't be
donwported at all).

Instead of smuggling this fix into another downport, it has been
argued (https://mail.openjdk.java.net/pipermail/jdk-updates-dev/2020-February/002533.html)
that it is cleaner to create an explicit issue for fixing it in 11u.

The fix is trivial (that's why it was done as part of JDK-8210958
without an extra bug ID) and only affects running "make test-make".

Thank you and best regards,
Volker