Restore the libiberty component of commit 50ad1254d5.

This commit has not yet been applied to the master sources in the gcc repository.
It was submitted here: https://gcc.gnu.org/pipermail/gcc-patches/2021-July/574405.html
The commit allows options to be set for the AR and RANLIB programs used when building libiberty, which in turn allows building with LTO enabled.

libiberty/Makefile.in

@@ -49,13 +49,13 @@ mkinstalldirs = $(SHELL) $(libiberty_topdir)/mkinstalldirs
 # Some compilers can't handle cc -c blah.c -o foo/blah.o.
 OUTPUT_OPTION = @OUTPUT_OPTION@
 
-AR = @AR@
+AR = @AR@ @AR_PLUGIN_OPTION@
 AR_FLAGS = rc
 
 CC = @CC@
 CFLAGS = @CFLAGS@
 CPPFLAGS = @CPPFLAGS@
-RANLIB = @RANLIB@
+RANLIB = @RANLIB@ @RANLIB_PLUGIN_OPTION@
 MAKEINFO = @MAKEINFO@
 PERL = @PERL@
 
@@ -487,6 +487,7 @@ aclocal_deps = \
 	$(srcdir)/../config/acx.m4 \
 	$(srcdir)/../config/cet.m4 \
 	$(srcdir)/../config/enable.m4 \
+	$(srcdir)/../config/gcc-plugin.m4 \
 	$(srcdir)/../config/no-executables.m4 \
 	$(srcdir)/../config/override.m4 \
 	$(srcdir)/../config/picflag.m4 \

libiberty/aclocal.m4

@@ -15,6 +15,7 @@ m4_ifndef([AC_CONFIG_MACRO_DIRS], [m4_defun([_AM_CONFIG_MACRO_DIRS], [])m4_defun
 m4_include([../config/acx.m4])
 m4_include([../config/cet.m4])
 m4_include([../config/enable.m4])
+m4_include([../config/gcc-plugin.m4])
 m4_include([../config/no-executables.m4])
 m4_include([../config/picflag.m4])
 m4_include([../config/warnings.m4])

libiberty/configure

@@ -645,6 +645,8 @@ CPPFLAGS
 LDFLAGS
 CFLAGS
 CC
+RANLIB_PLUGIN_OPTION
+AR_PLUGIN_OPTION
 RANLIB
 AR
 host_os
@@ -2929,6 +2931,144 @@ else
 fi
 
 
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for -plugin option" >&5
+$as_echo_n "checking for -plugin option... " >&6; }
+
+plugin_names="liblto_plugin.so liblto_plugin-0.dll cyglto_plugin-0.dll"
+plugin_option=
+for plugin in $plugin_names; do
+  plugin_so=`${CC} ${CFLAGS} --print-prog-name $plugin`
+  if test x$plugin_so = x$plugin; then
+    plugin_so=`${CC} ${CFLAGS} --print-file-name $plugin`
+  fi
+  if test x$plugin_so != x$plugin; then
+    plugin_option="--plugin $plugin_so"
+    break
+  fi
+done
+if test -n "$ac_tool_prefix"; then
+  # Extract the first word of "${ac_tool_prefix}ar", so it can be a program name with args.
+set dummy ${ac_tool_prefix}ar; ac_word=$2
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+$as_echo_n "checking for $ac_word... " >&6; }
+if ${ac_cv_prog_AR+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  if test -n "$AR"; then
+  ac_cv_prog_AR="$AR" # Let the user override the test.
+else
+as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_exec_ext in '' $ac_executable_extensions; do
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
+    ac_cv_prog_AR="${ac_tool_prefix}ar"
+    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+  done
+IFS=$as_save_IFS
+
+fi
+fi
+AR=$ac_cv_prog_AR
+if test -n "$AR"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $AR" >&5
+$as_echo "$AR" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+
+fi
+if test -z "$ac_cv_prog_AR"; then
+  ac_ct_AR=$AR
+  # Extract the first word of "ar", so it can be a program name with args.
+set dummy ar; ac_word=$2
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+$as_echo_n "checking for $ac_word... " >&6; }
+if ${ac_cv_prog_ac_ct_AR+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  if test -n "$ac_ct_AR"; then
+  ac_cv_prog_ac_ct_AR="$ac_ct_AR" # Let the user override the test.
+else
+as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_exec_ext in '' $ac_executable_extensions; do
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
+    ac_cv_prog_ac_ct_AR="ar"
+    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+  done
+IFS=$as_save_IFS
+
+fi
+fi
+ac_ct_AR=$ac_cv_prog_ac_ct_AR
+if test -n "$ac_ct_AR"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_ct_AR" >&5
+$as_echo "$ac_ct_AR" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+  if test "x$ac_ct_AR" = x; then
+    AR=""
+  else
+    case $cross_compiling:$ac_tool_warned in
+yes:)
+{ $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: using cross tools not prefixed with host triplet" >&5
+$as_echo "$as_me: WARNING: using cross tools not prefixed with host triplet" >&2;}
+ac_tool_warned=yes ;;
+esac
+    AR=$ac_ct_AR
+  fi
+else
+  AR="$ac_cv_prog_AR"
+fi
+
+if test "${AR}" = "" ; then
+  as_fn_error $? "Required archive tool 'ar' not found on PATH." "$LINENO" 5
+fi
+touch conftest.c
+${AR} $plugin_option rc conftest.a conftest.c
+if test "$?" != 0; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: Failed: $AR $plugin_option rc" >&5
+$as_echo "$as_me: WARNING: Failed: $AR $plugin_option rc" >&2;}
+  plugin_option=
+fi
+rm -f conftest.*
+if test -n "$plugin_option"; then
+  PLUGIN_OPTION="$plugin_option"
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $plugin_option" >&5
+$as_echo "$plugin_option" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+if test -n "$PLUGIN_OPTION"; then
+  if $AR --help 2>&1 | grep -q "\--plugin"; then
+    AR_PLUGIN_OPTION="$PLUGIN_OPTION"
+
+  fi
+  if $RANLIB --help 2>&1 | grep -q "\--plugin"; then
+    RANLIB_PLUGIN_OPTION="$PLUGIN_OPTION"
+
+  fi
+fi
+
 # Add --enable-multilib to configure.
 # Default to --enable-multilib
 # Check whether --enable-multilib was given.

libiberty/configure.ac

@@ -108,6 +108,18 @@ dnl to call AC_CHECK_PROG.
 AC_CHECK_TOOL(AR, ar)
 AC_CHECK_TOOL(RANLIB, ranlib, :)
 
+GCC_PLUGIN_OPTION(PLUGIN_OPTION)
+if test -n "$PLUGIN_OPTION"; then
+  if $AR --help 2>&1 | grep -q "\--plugin"; then
+    AR_PLUGIN_OPTION="$PLUGIN_OPTION"
+    AC_SUBST(AR_PLUGIN_OPTION)
+  fi
+  if $RANLIB --help 2>&1 | grep -q "\--plugin"; then
+    RANLIB_PLUGIN_OPTION="$PLUGIN_OPTION"
+    AC_SUBST(RANLIB_PLUGIN_OPTION)
+  fi
+fi
+
 dnl When switching to automake, replace the following with AM_ENABLE_MULTILIB.
 # Add --enable-multilib to configure.
 # Default to --enable-multilib