CrayPE fix for mercury (#23514)

allow for multiple definitions at link time (for CCE's linker)


Co-authored-by: Tamara Dahlgren <35777542+tldahlgren@users.noreply.github.com>

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

@@ -59,6 +59,12 @@ class Mercury(CMakePackage):
     # See https://github.com/mercury-hpc/mercury/issues/299
     patch('fix-cmake-3.15-check_symbol_exists.patch', when='@1.0.0:1.0.1')
 
+    def flag_handler(self, name, flags):
+        if self.spec.satisfies('%cce'):
+            if name == 'ldflags':
+                flags.append('-Wl,-z,muldefs')
+            return (None, None, flags)
+
     def cmake_args(self):
         """Populate cmake arguments for Mercury."""
         spec = self.spec