[glibc/azanella/clang] Fix -fno-unit-at-a-time for clang

[Adhemerval Zanella <azanella@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=66aee60f16119c792767ad0e188aa81de740c81c

commit 66aee60f16119c792767ad0e188aa81de740c81c
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Wed Mar 9 16:06:34 2022 -0300

    Fix -fno-unit-at-a-time for clang
    
    It does not support the option.

Diff:
---
 configure    | 32 +++++++++++++++++++++++++++++++-
 configure.ac | 20 +++++++++++++++++++-
 2 files changed, 50 insertions(+), 2 deletions(-)

diff --git a/configure b/configure
index c57b6e8785..e810148d43 100755
--- a/configure
+++ b/configure
@@ -6344,10 +6344,40 @@ rm -f conftest*
 fi
 { $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_fno_toplevel_reorder" >&5
 $as_echo "$libc_cv_fno_toplevel_reorder" >&6; }
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for -fno-unit-at-a-time" >&5
+$as_echo_n "checking for -fno-unit-at-a-time... " >&6; }
+if ${libc_cv_fno_unit_at_a_time+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat > conftest.c <<EOF
+int foo;
+EOF
+if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS -S -Werror -fno-unit-at-a-time conftest.c
+		   1>&5'
+  { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; }
+then
+  libc_cv_fno_unit_at_a_time=yes
+else
+  libc_cv_fno_unit_at_a_time=no
+fi
+rm -f conftest*
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_fno_unit_at_a_time" >&5
+$as_echo "$libc_cv_fno_unit_at_a_time" >&6; }
+
 if test $libc_cv_fno_toplevel_reorder = yes; then
   fno_unit_at_a_time="-fno-toplevel-reorder -fno-section-anchors"
 else
-  fno_unit_at_a_time=-fno-unit-at-a-time
+  if test $libc_cv_fno_unit_at_a_time == yes; then
+    fno_unit_at_a_time="-fno-unit-at-a-time"
+  else
+    fno_unit_at_a_time=
+  fi
 fi
 
 
diff --git a/configure.ac b/configure.ac
index 5eeabfaa6d..ecef952dee 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1490,10 +1490,28 @@ else
   libc_cv_fno_toplevel_reorder=no
 fi
 rm -f conftest*])
+
+AC_CACHE_CHECK(for -fno-unit-at-a-time, libc_cv_fno_unit_at_a_time, [dnl
+cat > conftest.c <<EOF
+int foo;
+EOF
+if AC_TRY_COMMAND([${CC-cc} $CFLAGS $CPPFLAGS -S -Werror -fno-unit-at-a-time conftest.c
+		   1>&AS_MESSAGE_LOG_FD])
+then
+  libc_cv_fno_unit_at_a_time=yes
+else
+  libc_cv_fno_unit_at_a_time=no
+fi
+rm -f conftest*])
+
 if test $libc_cv_fno_toplevel_reorder = yes; then
   fno_unit_at_a_time="-fno-toplevel-reorder -fno-section-anchors"
 else
-  fno_unit_at_a_time=-fno-unit-at-a-time
+  if test $libc_cv_fno_unit_at_a_time == yes; then
+    fno_unit_at_a_time="-fno-unit-at-a-time"
+  else
+    fno_unit_at_a_time=
+  fi
 fi
 AC_SUBST(fno_unit_at_a_time)