RFR: JDK-8073021: add native code coverage target into makefiles

[Tim Bell]

Erik:

>> Hello,
>>
>> Please review this patch. A new configure parameter 
>> --enable-native-coverage is introduced. Setting it only works when 
>> using gcc, for now. It adds '-fprofile-arcs -ftest-coverage 
>> -fno-inline' to compiler flags and '-fprofile-arcs' to linker flags, 
>> for both jdk and hotspot native libraries (but not for native test 
>> libraries). Setting this causes gcc to generate code coverage 
>> instrumentation into the binaries as well as generating a .gcno file 
>> for each object file created. The gcno files are needed for 
>> converting gathered coverage data into a comprehensible report. When 
>> native coverage is active, a new image containing the .gcno files is 
>> created by the images target.
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8073021
>> Webrev: http://cr.openjdk.java.net/~erikj/8073021/webrev.root.01/
>
> Looks good to me.
>
> /Magnus

Looks good to me as well.

Tim