[PATCH] io: Use gnulib fts implementation (BZ 22944, BZ 20331)

[Bruno Haible]

Florian Weimer wrote:
> > Like the directory resolv/nss_dns/ under resolv/.
> > Or like the directories nss/nss_compat/, nss/nss_db/, nss/nss_files/
> > under nss/.
> 
> That requires using vpath.  The glibc build system is not really
> compatible with that.

What do you mean by that? I see more than 20 uses of 'vpath' in glibc:

$ grep -rn ^vpath . | sort
./catgets/Makefile:58:vpath %.c ../locale/programs
./elf/Makefile:2242:vpath localplt.data $(+sysdep_dirs)
./elf/Makefile:241:vpath %.c ../locale/programs
./hesiod/Makefile:29:vpath %.c nss_hesiod
./iconv/Makefile:31:vpath %.c ../locale/programs ../intl
./localedata/Makefile:32:vpath %.c tests-mbwc
./localedata/Makefile:33:vpath %.h tests-mbwc
./locale/Makefile:105:vpath %.c programs
./locale/Makefile:106:vpath %.h programs
./locale/Makefile:107:vpath %.gperf programs
./login/Makefile:75:vpath %.c programs
./mach/Machrules:102:vpath Machrules ../mach    # Find ourselves.
./mach/Machrules:148:vpath %_server.c $(addprefix $(objpfx),$(sort $(dir $(server-interfaces))))
./Makefile:528:vpath c++-types.data $(+sysdep_dirs)
./Makefile:79:vpath %.h $(subdir-dirs)
./Makerules:1194:vpath %.input $(sysdirs)
./Makerules:1251:vpath %.abilist $(+sysdep_dirs)
./Makerules:280:vpath %.sym $(sysdirs)
./Makerules:69:vpath %.h $(subst $(empty) ,:,$(strip $(common-objpfx) $(objpfx) \
./Makerules:73:vpath %.x $(subst $(empty) ,:,$(strip $(common-objpfx) $(objpfx) \
./nscd/Makefile:32:vpath %.c ../locale/programs
./nss/Makefile:398:vpath %.c $(subdir-dirs) ../locale/programs ../intl
./resolv/Makefile:226:vpath %.c nss_dns
./sysdeps/ieee754/ldbl-64-128/Makefile:9:vpath tst-scanf-format-ldouble-$(1).input ../sysdeps/ieee754/ldbl-128