[8u] RFR: 8262864: No debug symbols in image for Windows --with-native-debug-symbols=external

[Andrew Leonard]

Hi,
Please can I get reviews for this patch to fix the creation of jdk8u
Windows debug files (.map, .pdb) when using
--with-native-debug-symbols=external. A recent fix resolved this for
non-Windows (https://bugs.openjdk.java.net/browse/JDK-8252395), this fixes
Windows and also a minor issue with the other platforms that JDK-8252395
didn't quite fix.
webrev: https://cr.openjdk.java.net/~aleonard/8262864/webrev.00/
bug: https://bugs.openjdk.java.net/browse/JDK-8262864
Thanks
Andrew