netcdf-cxx4: Update to use CPPFLAGS (#8148)

* Fix bug; don't know why this ever worked in the first place.

* Add fix to netcdf-fortran too; flake8

* Simplify configure_args()

* netcdf-fortran: simplify that too

var/spack/repos/builtin/packages/netcdf-cxx4/package.py

@@ -41,6 +41,9 @@ class NetcdfCxx4(AutotoolsPackage):
 
     force_autoreconf = True
 
+    def configure_args(self):
+        return ['CPPFLAGS=-I' + self.spec['netcdf'].prefix.include]
+
     @property
     def libs(self):
         shared = True

var/spack/repos/builtin/packages/netcdf-fortran/package.py

@@ -36,6 +36,9 @@ class NetcdfFortran(AutotoolsPackage):
 
     depends_on('netcdf')
 
+    def configure_args(self):
+        return ['CPPFLAGS=-I' + self.spec['netcdf'].prefix.include]
+
     @property
     def libs(self):
         libraries = ['libnetcdff']