Kluge to get the gfortran linker to work correctly for SciPy on Big Sur. (#20367)

* Kluge to get the gfortran linker to work correctly on Big Sur.

* Fixed formatting error; stetting the other.

* Removed spaces.

* Added comment, mainly to re-trigger Spack CI.

var/spack/repos/builtin/packages/py-scipy/package.py

@@ -3,6 +3,8 @@
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
+import platform
+
 
 class PyScipy(PythonPackage):
     """SciPy (pronounced "Sigh Pie") is a Scientific Library for Python.
@@ -85,6 +87,12 @@ def setup_build_environment(self, env):
         if self.spec.satisfies('@:1.4 %gcc@10:'):
             env.set('FFLAGS', '-fallow-argument-mismatch')
 
+        # Kluge to get the gfortran linker to work correctly on Big
+        # Sur, at least until a gcc release > 10.2 is out with a fix.
+        # (There is a fix in their development tree.)
+        if platform.mac_ver()[0][0:2] == '11':
+            env.set('MACOSX_DEPLOYMENT_TARGET', '10.15')
+
     def build_args(self, spec, prefix):
         args = []
         if spec.satisfies('%fj'):