RFR: JDK-8170878: JDK 9 fails to build when enabling Hotspot code coverage

[Erik Joelsson]

Hello,

The bundles and the jprt_bundles targets fail when enabling native code 
coverage in the build. Currently enabling code coverage is the only way 
to generate data for the "symbols" image (because we are still putting 
the actual debug symbols in the regular jdk/jre images).

One of the problems fixed is to add prerequisites to the symbols-image 
target so that it doesn't fail when code coverage is enabled.

The other, more serious problem was that when enabling code coverage, 
the symbols bundle is now constructed with files from two different base 
directories, but the recipe logic is only able to handle one base dir. I 
chose to fix the recipe logic to handle multiple base dirs. The recipe 
already had a couple of different paths/methods depending on the type of 
bundle to be built. Not all of them could easily be converted to support 
multiple roots, so I reordered them and adjusted the conditionals so 
that the most optimal method is chosen given the new valid constraint.

Bug: https://bugs.openjdk.java.net/browse/JDK-8170878

Webrev: http://cr.openjdk.java.net/~erikj/8170878/webrev.01/

/Erik