RFR: 8002034 and 8001756 - FDS changes mainly re cross-compiling

[David Holmes]

http://cr.openjdk.java.net/~dholmes/8002034/webrev/

This mainly addresses

JDK-8002034 Allow Full Debug Symbols when cross-compiling

The initial FDS work simply disables FDS when cross-compilation is 
involved. But we're now ready to deal with the cross-compilation case 
(and even if we weren't these changes would be fine anyway). So if FDS 
is initially enabled we will rely on ALT_OBJCOPY being set to the 
correct value for cross-compilation; and we don't set the default 
OBJCOPY in that case. So if you do nothing when cross-compiling OBJCOPY 
will be empty and that will cause the build to disable FDS, just as if 
the OBJCOPY command was not found.

As this is the same code that causes:

JDK-8001756 Hotspot makefiles report missing OBJCOPY command in the 
wrong circumstances

I also fixed this by moving the OBJCOPY checks inside the 
ENABLE_FULL_DEBUG_SYMBOLS=1 conditional. Basically unless we are asking 
for FDS we shouldn't complain if the OBJCOPY command is not found.

This will be pushed to the hotspot-emb repo as it is needed there ASAP.

I'll be doing a similar change, under 8002040, for the JDK side of things.

Thanks,
David