Patch libtool when using the Arm compiler (#12004)

* Patch libtool when using the arm, clang, and fujitsu compilers

If libtool does not have values for linker/pic flags, patch them in

lib/spack/spack/build_systems/autotools.py

@@ -5,10 +5,12 @@
 
 
 import inspect
+import fileinput
 import os
 import os.path
 import shutil
 import stat
+import sys
 from subprocess import PIPE
 from subprocess import check_call
 
@@ -56,6 +58,9 @@ class AutotoolsPackage(PackageBase):
     build_system_class = 'AutotoolsPackage'
     #: Whether or not to update ``config.guess`` on old architectures
     patch_config_guess = True
+    #: Whether or not to update ``libtool``
+    #: (currently only for Arm/Clang/Fujitsu compilers)
+    patch_libtool = True
 
     #: Targets for ``make`` during the :py:meth:`~.AutotoolsPackage.build`
     #: phase
@@ -148,6 +153,25 @@ def _do_patch_config_guess(self):
 
         raise RuntimeError('Failed to find suitable config.guess')
 
+    @run_after('configure')
+    def _do_patch_libtool(self):
+        """If configure generates a "libtool" script that does not correctly
+        detect the compiler (and patch_libtool is set), patch in the correct
+        flags for the Arm, Clang/Flang, and Fujitsu compilers."""
+
+        libtool = os.path.join(self.build_directory, "libtool")
+        if self.patch_libtool and os.path.exists(libtool):
+            if self.spec.satisfies('%arm') or self.spec.satisfies('%clang') \
+                    or self.spec.satisfies('%fj'):
+                for line in fileinput.input(libtool, inplace=True):
+                    # Replace missing flags with those for Arm/Clang
+                    if line == 'wl=""\n':
+                        line = 'wl="-Wl,"\n'
+                    if line == 'pic_flag=""\n':
+                        line = 'pic_flag="{0}"\n'\
+                               .format(self.compiler.pic_flag)
+                    sys.stdout.write(line)
+
     @property
     def configure_directory(self):
         """Returns the directory where 'configure' resides.