build: drop the use of XC_AMEND_DISTCLEAN

Because automake used to delete depdirs at once (.deps) and there was an issue
with portability, curl's XC_AMEND_DISTCLEAN greps the Makefiles in an attempt
to build a list of all depfiles and delete them individually instead.

Since commit 08849db866b44510f6b8fd49e313c91a43a3dfd3, automake switched from
deleting directories to individual files. curl's custom logic now finds a lot
more results with the grep (the filtering of these results isn't great), which
causes a massive bloating of the Makefile in the order of O(n^2).

Also remove now-unused XC_AMEND_DISTCLEAN macro group

References: https://github.com/curl/curl/issues/9843
References: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=59288

Reported-by: Ilmari Lauhakangas
Fixes #9843
Closes #10661

configure.ac

@@ -4665,8 +4665,6 @@ AC_OUTPUT
 
 CURL_GENERATE_CONFIGUREHELP_PM
 
-XC_AMEND_DISTCLEAN([lib src tests/unit tests/server tests/libtest docs/examples])
-
 AC_MSG_NOTICE([Configured to build curl/libcurl:
 
   Host setup:       ${host}

m4/xc-am-iface.m4

@@ -83,172 +83,3 @@ m4_ifdef([AM_INIT_AUTOMAKE],
 dnl
 m4_define([$0], [])[]dnl
 ])
-
-
-dnl _XC_AMEND_DISTCLEAN_BODY ([LIST-OF-SUBDIRS])
-dnl -------------------------------------------------
-dnl Private macro.
-dnl
-dnl This macro performs shell code embedding into
-dnl configure script in order to modify distclean
-dnl and maintainer-clean targets of makefiles which
-dnl are located in given list of subdirs.
-dnl
-dnl See XC_AMEND_DISTCLEAN comments for details.
-
-m4_define([_XC_AMEND_DISTCLEAN_BODY],
-[dnl
-## ---------------------------------- ##
-##  Start of distclean amending code  ##
-## ---------------------------------- ##
-
-for xc_subdir in [$1]
-do
-
-if test ! -f "$xc_subdir/Makefile"; then
-  echo "$xc_msg_err $xc_subdir/Makefile file not found. $xc_msg_abrt" >&2
-  exit 1
-fi
-
-# Fetch dependency tracking file list from Makefile include lines.
-
-xc_inc_lines=`grep '^include .*(DEPDIR)' "$xc_subdir/Makefile" 2>/dev/null`
-xc_cnt_words=`echo "$xc_inc_lines" | wc -w | tr -d "$xc_space$xc_tab"`
-
-# --disable-dependency-tracking might have been used, consequently
-# there is nothing to amend without a dependency tracking file list.
-
-if test $xc_cnt_words -gt 0; then
-
-AC_MSG_NOTICE([amending $xc_subdir/Makefile])
-
-# Build Makefile specific patch hunk.
-
-xc_p="$xc_subdir/xc_patch.tmp"
-
-xc_rm_depfiles=`echo "$xc_inc_lines" \
-  | $SED 's%include%	-rm -f%' 2>/dev/null`
-
-xc_dep_subdirs=`echo "$xc_inc_lines" \
-  | $SED 's%include[[ ]][[ ]]*%%' 2>/dev/null \
-  | $SED 's%(DEPDIR)/.*%(DEPDIR)%' 2>/dev/null \
-  | sort | uniq`
-
-echo "$xc_rm_depfiles" >$xc_p
-
-for xc_dep_dir in $xc_dep_subdirs; do
-  echo "${xc_tab}@xm_dep_cnt=\`ls $xc_dep_dir | wc -l 2>/dev/null\`; \\"            >>$xc_p
-  echo "${xc_tab}if test \$\$xm_dep_cnt -eq 0 && test -d $xc_dep_dir; then \\"      >>$xc_p
-  echo "${xc_tab}  rm -rf $xc_dep_dir; \\"                                          >>$xc_p
-  echo "${xc_tab}fi"                                                                >>$xc_p
-done
-
-# Build Makefile patching sed scripts.
-
-xc_s1="$xc_subdir/xc_script_1.tmp"
-xc_s2="$xc_subdir/xc_script_2.tmp"
-xc_s3="$xc_subdir/xc_script_3.tmp"
-
-cat >$xc_s1 <<\_EOT
-/^distclean[[ ]]*:/,/^[[^	]][[^	]]*:/{
-  s/^.*(DEPDIR)/___xc_depdir_line___/
-}
-/^maintainer-clean[[ ]]*:/,/^[[^	]][[^	]]*:/{
-  s/^.*(DEPDIR)/___xc_depdir_line___/
-}
-_EOT
-
-cat >$xc_s2 <<\_EOT
-/___xc_depdir_line___$/{
-  N
-  /___xc_depdir_line___$/D
-}
-_EOT
-
-cat >$xc_s3 <<_EOT
-/^___xc_depdir_line___/{
-  r $xc_p
-  d
-}
-_EOT
-
-# Apply patch to Makefile and cleanup.
-
-$SED -f "$xc_s1" "$xc_subdir/Makefile"      >"$xc_subdir/Makefile.tmp1"
-$SED -f "$xc_s2" "$xc_subdir/Makefile.tmp1" >"$xc_subdir/Makefile.tmp2"
-$SED -f "$xc_s3" "$xc_subdir/Makefile.tmp2" >"$xc_subdir/Makefile.tmp3"
-
-if test -f "$xc_subdir/Makefile.tmp3"; then
-  mv -f "$xc_subdir/Makefile.tmp3" "$xc_subdir/Makefile"
-fi
-
-test -f "$xc_subdir/Makefile.tmp1" && rm -f "$xc_subdir/Makefile.tmp1"
-test -f "$xc_subdir/Makefile.tmp2" && rm -f "$xc_subdir/Makefile.tmp2"
-test -f "$xc_subdir/Makefile.tmp3" && rm -f "$xc_subdir/Makefile.tmp3"
-
-test -f "$xc_p"  && rm -f "$xc_p"
-test -f "$xc_s1" && rm -f "$xc_s1"
-test -f "$xc_s2" && rm -f "$xc_s2"
-test -f "$xc_s3" && rm -f "$xc_s3"
-
-fi
-
-done
-
-## -------------------------------- ##
-##  End of distclean amending code  ##
-## -------------------------------- ##
-dnl
-m4_define([$0], [])[]dnl
-])
-
-
-dnl XC_AMEND_DISTCLEAN ([LIST-OF-SUBDIRS])
-dnl -------------------------------------------------
-dnl Public macro.
-dnl
-dnl This macro embeds shell code into configure script
-dnl that amends, at configure runtime, the distclean
-dnl and maintainer-clean targets of Makefiles located
-dnl in all subdirs given in the mandatory white-space
-dnl separated list argument.
-dnl
-dnl Embedding only takes place when using automake 1.14
-dnl or newer, otherwise amending code is not included
-dnl in generated configure script.
-dnl
-dnl distclean and maintainer-clean targets are modified
-dnl to avoid unconditional removal of dependency subdirs
-dnl which triggers distclean and maintainer-clean errors
-dnl when using automake 'subdir-objects' option along
-dnl with per-target objects and source files existing in
-dnl multiple subdirs used for different build targets.
-dnl
-dnl New behavior first removes each dependency tracking
-dnl file independently, and only removes each dependency
-dnl subdir when it finds out that it no longer holds any
-dnl dependency tracking file.
-dnl
-dnl When configure option --disable-dependency-tracking
-dnl is used no amending takes place given that there are
-dnl no dependency tracking files.
-
-AC_DEFUN([XC_AMEND_DISTCLEAN],
-[dnl
-AC_PREREQ([2.50])dnl
-dnl
-m4_ifdef([_AC_OUTPUT_MAIN_LOOP],
-  [m4_provide_if([_AC_OUTPUT_MAIN_LOOP], [],
-    [m4_fatal([call to AC_OUTPUT needed before $0])])])dnl
-dnl
-m4_if([$#], [1], [], [m4_fatal([$0: wrong number of arguments])])dnl
-m4_if([$1], [], [m4_fatal([$0: missing argument])])dnl
-dnl
-AC_REQUIRE([XC_CONFIGURE_PREAMBLE])dnl
-dnl
-m4_ifdef([_AM_PROG_CC_C_O],
-[
-_XC_AMEND_DISTCLEAN_BODY([$1])
-])dnl
-m4_define([$0], [])[]dnl
-])