Updated from libtool.m4 patch:

[PATCH] Improve macOS version detection to support macOS 11 and simplify legacy logic

Signed-off-by: Jeremy Huddleston Sequoia <jeremyhu@apple.com>

--- hwloc/configure.old	2020-11-25 16:03:04.225097149 +0100
+++ hwloc/configure	2020-11-25 16:02:29.368995613 +0100
@@ -8846,16 +8846,13 @@
       _lt_dar_allow_undefined='$wl-undefined ${wl}suppress' ;;
     darwin1.*)
       _lt_dar_allow_undefined='$wl-flat_namespace $wl-undefined ${wl}suppress' ;;
-    darwin*) # darwin 5.x on
-      # if running on 10.5 or later, the deployment target defaults
-      # to the OS version, if on x86, and 10.4, the deployment
-      # target defaults to 10.4. Don't you love it?
-      case ${MACOSX_DEPLOYMENT_TARGET-10.0},$host in
-	10.0,*86*-darwin8*|10.0,*-darwin[91]*)
-	  _lt_dar_allow_undefined='$wl-undefined ${wl}dynamic_lookup' ;;
-	10.[012][,.]*)
-	  _lt_dar_allow_undefined='$wl-flat_namespace $wl-undefined ${wl}suppress' ;;
-	10.*)
+    darwin*)
+      # Open MPI patched for Darwin / MacOS Big Sur.  See
+      # http://lists.gnu.org/archive/html/bug-libtool/2015-07/msg00001.html
+      case ${MACOSX_DEPLOYMENT_TARGET},$host in
+	10.[012],*|,*powerpc*)
+	  _lt_dar_allow_undefined='${wl}-flat_namespace ${wl}-undefined ${wl}suppress' ;;
+	*)
 	  _lt_dar_allow_undefined='$wl-undefined ${wl}dynamic_lookup' ;;
       esac
     ;;
