RFR(XXS) 8231902: Build of jdk.internal.vm.compiler.management/module-info.java.extra failed

[dean.long at oracle.com]

https://bugs.openjdk.java.net/browse/JDK-8231902
http://cr.openjdk.java.net/~dlong/8231902/webrev/

A recent upstream Graal change causes the META-INF/providers directory 
to contain only a single file, causing the $(GREP) command to not 
prepend the filename to the output.  The simple fix is to create an 
empty file in the directory.

dl