All macosx builds in CI currently fail. This is caused by in issue with
JDK-8201483 which leaves the JVM_VARIANTS_server variable empty. The
construct used to subtract one set of strings from another doesn't work
quite as expected with bsd grep.
result=`$GREP -Fvx "$legal_values" <<< "$values_to_check" | $GREP -v '^$'`
If the set to subtract ($legal_values) is empty, gnu grep returns all
values (as expected) while bsd grep returns nothing. To fix this I've
added an explicit check for the base case of legal_values being empty.
This seems to make --with-jvm-features work correctly on macosx and
still work correctly on Linux. A verification distributed build is under