bpo-45405: Prevent internal configure error when running configure with recent versions of clang. (GH-28845) (GH-31889)

Change the configure logic to function properly on macOS when the compiler
outputs a platform triplet for option --print-multiarch.
The Apple Clang included with Xcode 13.3 now supports --print-multiarch
causing configure to fail without this change.

Co-authored-by: Ned Deily <[email protected]>
(cherry picked from commit 9c47667)

Co-authored-by: David Bohman <[email protected]>

Automerge-Triggered-By: GH:ned-deily
(cherry picked from commit 9901d15)

Co-authored-by: Miss Islington (bot) <[email protected]>

Author: ned-deily

Misc/NEWS.d/next/Build/2021-10-11-16-27-38.bpo-45405.iSfdW5.rst

@@ -0,0 +1,2 @@
+Prevent ``internal configure error`` when running ``configure``
+with recent versions of clang.  Patch by David Bohman.

configure

@@ -5160,9 +5160,6 @@ $as_echo "$as_me:
 fi
 
 
-MULTIARCH=$($CC --print-multiarch 2>/dev/null)
-
-
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for the platform triplet based on compiler characteristics" >&5
 $as_echo_n "checking for the platform triplet based on compiler characteristics... " >&6; }
 cat >> conftest.c <<EOF
@@ -5321,6 +5318,11 @@ $as_echo "none" >&6; }
 fi
 rm -f conftest.c conftest.out
 
+if test x$PLATFORM_TRIPLET != xdarwin; then
+  MULTIARCH=$($CC --print-multiarch 2>/dev/null)
+fi
+
+
 if test x$PLATFORM_TRIPLET != x && test x$MULTIARCH != x; then
   if test x$PLATFORM_TRIPLET != x$MULTIARCH; then
     as_fn_error $? "internal configure error for the platform triplet, please file a bug report" "$LINENO" 5

configure.ac

@@ -719,9 +719,6 @@ then
 fi
 
 
-MULTIARCH=$($CC --print-multiarch 2>/dev/null)
-AC_SUBST(MULTIARCH)
-
 AC_MSG_CHECKING([for the platform triplet based on compiler characteristics])
 cat >> conftest.c <<EOF
 #undef bfin
@@ -877,6 +874,11 @@ else
 fi
 rm -f conftest.c conftest.out
 
+if test x$PLATFORM_TRIPLET != xdarwin; then
+  MULTIARCH=$($CC --print-multiarch 2>/dev/null)
+fi
+AC_SUBST(MULTIARCH)
+
 if test x$PLATFORM_TRIPLET != x && test x$MULTIARCH != x; then
   if test x$PLATFORM_TRIPLET != x$MULTIARCH; then
     AC_MSG_ERROR([internal configure error for the platform triplet, please file a bug report])