dealii: add nanoflann, sundials and adol-c plus fixes on macOS (#5175)

* expat: fix build on macOS

* nanoflann: add new package

* sundials: fix compilation on macOS with clang+gfortran

* adol-c: add 2.6.3

* dealii: add adol-c, nanoflann, sundials and 8.5.1

* sundials: minor cleanup

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

@@ -23,6 +23,7 @@
 # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 ##############################################################################
 from spack import *
+import sys
 
 
 class Expat(AutotoolsPackage):
@@ -39,7 +40,7 @@ class Expat(AutotoolsPackage):
     # someone's asking for an older version and also libbsd.
     # In order to install an older version, you'll need to add
     # `~libbsd`.
-    variant('libbsd', default=True,
+    variant('libbsd', default=sys.platform != 'darwin',
             description="Use libbsd (for high quality randomness)")
     depends_on('libbsd', when="@2.2.1:+libbsd")