In SetupProcessMarkdown, if a POST_PROCESS command is given, there is a
potential race. This is caused by the call to ExecuteWithLog in the
recipe for the post process command where the command redirects stdout
to a file. ExecuteWithLog documents that if such a construct is used,
then the command must be run in a sub shell (by putting it between
parentheses) (see JDK-8158629).
This patch adds parentheses around the affect command. I have verified
that the exploded image no longer gets any empty man pages. This fix is
intended for JDK 13.
Bug: https://bugs.openjdk.java.net/browse/JDK-8226269
Webrev: http://cr.openjdk.java.net/~erikj/8226269/webrev.01/
/Erik
