configury: add support for flang.

flang is currently not supported by libtool, so once configure has been invoked,
it is necessary to manually hack the generated libtool as described at
https://developer.arm.com/products/software-development-tools/hpc/resources/porting-and-tuning/building-openmpi-with-arm-compiler

This commit hacks the generated configure automatically in autogen.pl

The libtool patch has been submitted upstream and is available at https://savannah.gnu.org/patch/index.php?9442

Signed-off-by: Gilles Gouaillardet <gilles@rist.or.jp>

autogen.pl

@@ -975,6 +975,28 @@ sub patch_autotools_output {
     # Below is essentially an upstream patch for Libtool which we want
     # made available to Open MPI users running older versions of Libtool
 
+    foreach my $tag (("", "_FC")) {
+
+        # We have to change the search pattern and substitution on each
+        # iteration to take into account the tag changing
+        my $search_string = '# icc used to be incompatible with GCC.\n\s+' .
+                            '# ICC 10 doesn\047t accept -KPIC any more.\n.*\n\s+' .
+	                    "lt_prog_compiler_wl${tag}=";
+        my $replace_string = "# Flang compiler
+      *flang)
+	lt_prog_compiler_wl${tag}='-Wl,'
+	lt_prog_compiler_pic${tag}='-fPIC -DPIC'
+	lt_prog_compiler_static${tag}='-static'
+        ;;
+      # icc used to be incompatible with GCC.
+      # ICC 10 doesn't accept -KPIC any more.
+      icc* | ifort*)
+	lt_prog_compiler_wl${tag}=";
+
+        push(@verbose_out, $indent_str . "Patching configure for flang Fortran ($tag)\n");
+        $c =~ s/$search_string/$replace_string/;
+    }
+
     foreach my $tag (("", "_FC")) {
 
         # We have to change the search pattern and substitution on each