RFR: JDK-8075236: Change layout of gcov .gcno files in symbols image

[Erik Joelsson]

Hello,

In JDK-8073021 I added support for compiling with gcov support for 
native code coverage. When trying to use this it was discovered that the 
file layout in the new symbols image need to exactly match the layout of 
the .gcno files in the build directory. Otherwise the runtime data files 
created by gcov will not match properly.

I originally tried to tidy up the layout in the symbols file into:

symbols/gcov/hotspot/{client,server}/*.gcno
symbols/gcov/jdk/$(module)/$(lib)/*.gcno

What we actually need is the (internal) layout of the intermediate build 
results:

symbols/gcov/hotspot/linux_amd64_compiler2/product/*.gcno
symbols/gcov/support/native/$(module)/$(lib)/*.gcno

Our internal layout for intermediate build results is not something we 
want to export as an API, but in this case, the file layout just has to 
match the paths that get encoded into the binaries.

Bug: https://bugs.openjdk.java.net/browse/JDK-8075236
Webrev: http://cr.openjdk.java.net/~erikj/8075236/webrev.root.01/

/Erik