RFR: JDK-8151619: genSocketOptionRegistry.exe always relinked on Windows

[Erik Joelsson]

The build tool genSocketOptionRegistry.exe is always relinked on Windows 
at every rebuild. This causes a long chain of unnecessary rebuilding, 
completely destroying incremental build performance.

The underlying cause of this is the enabling of debug symbols everywhere 
without properly handling the debug symbol flags for Windows. 
SetupNativeCompilation in this case thinks debug symbols are to be 
generated and sets up dependencies based on that, but the compile and 
link command lines are not setup to generate them. Since they aren't 
there, the linking is redone each build.

My fix removes -Zi from C*FLAGS_JDKLIB and -debug from LDFLAGS_JDKLIB 
and adds them to the *FLAGS_DEBUG_SYMBOLS variables instead, just as 
have been done for all other platforms. I also move the .pdb files 
generated for object files to a separate sub directory to avoid name 
clashes if a source file and the resulting executable/lib has the same name.

When running a compare build, sawindbg.dll differs on Windows x86 
because it historically sets -ZI in CFLAGS, which is now overridden in 
this patch. I very much doubt there is any need to use -ZI instead of 
-Zi so also removing that flag from sawindb to not cause confusion about 
what is actually in effect.

Bug: https://bugs.openjdk.java.net/browse/JDK-8151619
Webrev: http://cr.openjdk.java.net/~erikj/8151619/webrev.01/

/Erik