spades: add conflict with older gcc (#9640)

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

@@ -21,6 +21,9 @@ class Spades(CMakePackage):
     depends_on('zlib')
     depends_on('bzip2')
 
+    # SPAdes will explicitly not compile with gcc < 5.3.0
+    conflicts('%gcc@:5.2.9')
+
     conflicts('%gcc@7.1.0:', when='@:3.10.1')
 
     root_cmakelists_dir = 'src'