RFR: JDK-8160334: Building --with-parfait= fails with No rule to make target 'PARFAIT_NATIVEJMOD

[Erik Joelsson]

When building using a special Oracle internal tool, the value of the 
JMOD_CMD variable has an environment variable assignment added to it 
(SOMETHING_FOO=foo /path/to/jmod). This causes the build to break in 
jmod creation, because the value of JMOD_CMD is used as a prerequisite 
in a rule declaration. This patch adds a wildcard to filter out any non 
files from the variable JMOD_CMD before trying to use the value as a 
prerequisite.

Bug: https://bugs.openjdk.java.net/browse/JDK-8160334

Webrev: http://cr.openjdk.java.net/~erikj/8160334/webrev.01/

/Erik