suite-sparse: add GCC version constraint (#9622)

Move suite-sparse gcc version constraint from dealii to suite-sparse
package and update it (gcc 4.9 is required as of version 5.2.0 rather
than 5.1.0). The constraint is now expressed as a conflict rather
than a dependency.

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

@@ -105,7 +105,6 @@ class Dealii(CMakePackage, CudaPackage):
     depends_on('lapack')
     depends_on('muparser')
     depends_on('suite-sparse')
-    depends_on('suite-sparse@:5.1.0', when='%gcc@:4.8.99')
     depends_on('tbb')
     depends_on('zlib')
 

var/spack/repos/builtin/packages/suite-sparse/package.py

@@ -46,6 +46,8 @@ class SuiteSparse(Package):
     # Fixes 'libgraphblas.so.2.0.1: undefined reference to `__fpclassify''
     patch('graphblas_libm_dep.patch', when='@5.2.0:5.2.99%clang')
 
+    conflicts('%gcc@:4.8', when='@5.2.0:', msg='gcc version must be at least 4.9 for suite-sparse@5.2.0:')
+
     def install(self, spec, prefix):
         # The build system of SuiteSparse is quite old-fashioned.
         # It's basically a plain Makefile which include an header