RFR: JDK-8217723 Switch ld from bfd to gold on gcc toolchain

[Martin Buchholz]

In our own wrappers around configure, we've introduced the concept of
a "developer mode".  But this thread suggests there are 3 populations
of users invoking configure:

1. release engineers
2. hotspot developers
3. java library developers

Category 1 doesn't care about edit-compile-debug cycle - they just
want to build a reliable high-performance jdk without pitfalls.  This
is the VAST MAJORITY of users, for whom we should design defaults in
configure.
Category 2 wants debug info and maybe incremental linking.  They might
cheat and rebuild only libjvm.so and drop that one file into a
previously built jdk as part of their development cycle.
Category 3 doesn't care about native debug symbols at all