Rather than implementing this at the wrapper level (which has been
attempted but not merged in # 252310 and # 205031), configuring GCC
directly with --enable-default-pie is simple and matches mainstream
distribution practices. Packages that cannot build with PIE can
explicitly pass -no-pie when needed, and mostly already do
due to the prevalence of GCCs built with this flag.
Requires followup to decide what to do with "pie" flag.
ccc56d1a79