driver: Don't imply -dD for -g3 -g0 [PR97989]

driver: Don't imply -dD for -g3 -g0 [PR97989]

The driver enables -dD when preprocessing when -g3 is specified, for obvious reasons
that we need the macros to be preserved somewhere for them to make up the debug
info.  But it enables it even if -g3 is later overridden to -g2, -g1 or -g0,
where we in the end don't emit .debug_mac{ros,info}.

The following patch passes -dD only if we'll need it.

2020-12-01  Jakub Jelinek  <jakub@redhat.com>

	PR debug/97989
	* gcc.c (cpp_unique_options): Add -dD if %:debug-level-gt(2)
	rather than g3|ggdb3|gstabs3|gxcoff3|gvms3.

	* gcc.dg/cpp/pr97989-1.c: New test.
	* gcc.dg/cpp/pr97989-2.c: New test.