arpack-ng: fix build with gcc@10: (#17131)

var/spack/repos/builtin/packages/arpack-ng/package.py

@@ -85,6 +85,12 @@ def libs(self):
             libraries, root=self.prefix, shared=True, recursive=True
         )
 
+    @when('@:3.7.0 %gcc@10:')
+    def setup_build_environment(self, env):
+        # version up to and including 3.7.0 are not ported to gcc 10
+        # https://github.com/opencollab/arpack-ng/issues/242
+        env.set('FFLAGS', '-fallow-argument-mismatch')
+
     @when('@3.4.0:')
     def install(self, spec, prefix):