[Ada] use -gnatd_A to disable .ali on -fcompare-debug recompile

[Ada] use -gnatd_A to disable .ali on -fcompare-debug recompile

for  gcc/ada/ChangeLog

	* gcc-interface/lang-specs.h (default_compilers): When given
	fcompare-debug-second, adjust auxbase like cc1, and pass
	gnatd_A.
	* gcc-interface/misc.c (flag_compare_debug): Remove variable.
	(gnat_post_options): Do not set it.
	* lib-writ.adb (flag_compare_debug): Remove import.
	(Write_ALI): Do not test it.

From-SVN: r264732