gmp: fix make check on catalina (#13201)

var/spack/repos/builtin/packages/gmp/package.py

@@ -30,10 +30,15 @@ class Gmp(AutotoolsPackage):
     # shared library support. Regenerating it fixes the issue.
     force_autoreconf = True
 
-    def configure_args(self):
-        args = ['--enable-cxx']
+    def flag_handler(self, name, flags):
+        # Work around macOS Catalina / Xcode 11 code generation bug
+        # (test failure t-toom53, due to wrong code in mpn/toom53_mul.o)
+        if self.spec.satisfies('os=catalina') and name == 'cflags':
+            flags.append('-fno-stack-check')
         # This flag is necessary for the Intel build to pass `make check`
-        if self.spec.compiler.name == 'intel':
-            args.append('CXXFLAGS=-no-ftz')
+        elif self.spec.satisfies('%intel') and name == 'cxxflags':
+            flags.append('-no-ftz')
+        return (flags, None, None)
 
-        return args
+    def configure_args(self):
+        return ['--enable-cxx']