bpo-38443: Check that the specified universal architectures work (GH-22910)

As [bpo-38443]() says the error message from configure when specifying --enable-universalsdk with a set of architectures that is not supported by the compiler is not very helpful.   This PR explicitly checks if the compiler works and bails out if it doesn't.
(cherry picked from commit 0f20bd9)

Co-authored-by: Ronald Oussoren <[email protected]>

Author: miss-islington

Misc/NEWS.d/next/macOS/2020-10-23-10-26-53.bpo-38443.vu64tl.rst

@@ -0,0 +1,2 @@
+The ``--enable-universalsdk`` and ``--with-universal-archs`` options for the
+configure script now check that the specified architectures can be used.

configure

@@ -7493,6 +7493,31 @@ $as_echo_n "checking which MACOSX_DEPLOYMENT_TARGET to use... " >&6; }
         { $as_echo "$as_me:${as_lineno-$LINENO}: result: $MACOSX_DEPLOYMENT_TARGET" >&5
 $as_echo "$MACOSX_DEPLOYMENT_TARGET" >&6; }
 
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking if specified universal architectures work" >&5
+$as_echo_n "checking if specified universal architectures work... " >&6; }
+        cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <stdio.h>
+int
+main ()
+{
+printf("%d", 42);
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+             as_fn_error $? "check config.log and use the '--with-universal-archs' option" "$LINENO" 5
+
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+
         # end of Darwin* tests
         ;;
     esac

configure.ac

@@ -1931,6 +1931,13 @@ yes)
         EXPORT_MACOSX_DEPLOYMENT_TARGET=''
         AC_MSG_RESULT($MACOSX_DEPLOYMENT_TARGET)
 
+        AC_MSG_CHECKING(if specified universal architectures work)
+        AC_LINK_IFELSE([AC_LANG_PROGRAM([[#include <stdio.h>]], [[printf("%d", 42);]])],
+            [AC_MSG_RESULT(yes)],
+            [AC_MSG_RESULT(no)
+             AC_MSG_ERROR(check config.log and use the '--with-universal-archs' option)
+        ])
+
         # end of Darwin* tests
         ;;
     esac