Exodus: skip the -G "Unix Makefiles" part (#5906)

* Exodus: skip the -G "Unix Makefiles" part

The problem is that spack passes -G "Unix Makefiles" into cmake, which normally
works. But in the Exodus package, it is being passed into a bash wrapper
script. In there, the $@ then loses the information about "Unix Makefiles"
being just one argument, and in effect passes -G Unix Makefiles into the cmake
(without quotes), and so cmake only sees -G Unix, and then fails. This is a
known problem with bash with no simple solutions. As a workaround, this patch
skips the first two arguments, i.e., -G and "Unix Makefiles". This makes it
work.

Fixes #5895.

* Port exodusii to cmake

The cmake options were taken from the cmake-exodus bash script and ported to
spack directly.

* Use variant forwarding to forward the 'mpi'

Now instead of

    spack install exodusii~mpi^netcdf~mpi^hdf5~mpi

one can just use

    spack install exodusii~mpi

var/spack/repos/builtin/packages/exodusii/cmake-exodus.patch

@@ -1,9 +0,0 @@
-diff --git a/cmake-exodus b/cmake-exodus
-index 67ccd34..9b749e3 100755
---- a/cmake-exodus
-+++ b/cmake-exodus
-@@ -1,3 +1,4 @@
-+#!/bin/bash
- EXTRA_ARGS=$@
- 
- ### The following assumes you are building in a subdirectory of ACCESS Root

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

@@ -27,11 +27,8 @@
 # TODO: Add support for a C++11 enabled installation that filters out the
 # TODO: "C++11-Disabled" flag (but only if the spec compiler supports C++11).
 
-# TODO: Use variant forwarding to forward the 'mpi' variant to the direct
-# TODO: dependencies 'hdf5' and 'netcdf'.
 
-
-class Exodusii(Package):
+class Exodusii(CMakePackage):
     """Exodus II is a C++/Fortran library developed to store and retrieve
        data for finite element analyses. It's used for preprocessing
        (problem definition), postprocessing (results visualization), and
@@ -52,18 +49,25 @@ class Exodusii(Package):
     depends_on('mpi', when='+mpi')
 
     # https://github.com/gsjaardema/seacas/blob/master/NetCDF-Mapping.md
-    depends_on('netcdf maxdims=65536 maxvars=524288')
-    depends_on('hdf5+shared')
+    depends_on('netcdf+mpi maxdims=65536 maxvars=524288', when='+mpi')
+    depends_on('netcdf~mpi maxdims=65536 maxvars=524288', when='~mpi')
+    depends_on('hdf5+shared+mpi', when='+mpi')
+    depends_on('hdf5+shared~mpi', when='~mpi')
 
-    patch('cmake-exodus.patch')
+    def cmake_args(self):
+        spec = self.spec
 
-    def install(self, spec, prefix):
         cc_path = spec['mpi'].mpicc if '+mpi' in spec else self.compiler.cc
         cxx_path = spec['mpi'].mpicxx if '+mpi' in spec else self.compiler.cxx
 
-        config_args = std_cmake_args[:]
-        config_args.extend([
+        options = [
             # General Flags #
+            '-DSEACASProj_ENABLE_SEACASExodus=ON',
+            '-DSEACASProj_ENABLE_TESTS=ON',
+            '-DBUILD_SHARED_LIBS:BOOL=ON',
+            '-DTPL_ENABLE_Netcdf:BOOL=ON',
+            '-DHDF5_NO_SYSTEM_PATHS=ON',
+            '-DSEACASProj_SKIP_FORTRANCINTERFACE_VERIFY_TEST:BOOL=ON',
             '-DSEACASProj_ENABLE_CXX11:BOOL=OFF',
             '-DSEACASProj_ENABLE_Zoltan:BOOL=OFF',
             '-DHDF5_ROOT:PATH={0}'.format(spec['hdf5'].prefix),
@@ -73,14 +77,6 @@ def install(self, spec, prefix):
             '-DTPL_ENABLE_MPI={0}'.format('ON' if '+mpi' in spec else 'OFF'),
             '-DCMAKE_C_COMPILER={0}'.format(cc_path),
             '-DCMAKE_CXX_COMPILER={0}'.format(cxx_path),
-        ])
+        ]
 
-        build_directory = join_path(self.stage.source_path, 'spack-build')
-        source_directory = self.stage.source_path
-
-        with working_dir(build_directory, create=True):
-            mcmake = Executable(join_path(source_directory, 'cmake-exodus'))
-            mcmake(*config_args)
-
-            make()
-            make('install')
+        return options