Add universal build_type variant to CMakePackage (#4797)

* Add universal build_type variant to CMakePackage
* Override build_type in some packages with different possible values
* Remove reference to no longer existent debug variant
* Update CBTF packages with new build_type variant
* Keep note on build size of LLVM

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

@@ -38,19 +38,10 @@ class Nalu(CMakePackage):
     version('master',
             git='https://github.com/NaluCFD/Nalu.git', branch='master')
 
-    variant('debug', default=False,
-            description='Builds a debug version')
-
     # Currently Nalu only builds static libraries; To be fixed soon
     depends_on('yaml-cpp+fpic~shared')
     depends_on('trilinos~shared+exodus+tpetra+muelu+belos+ifpack2+amesos2+zoltan+stk+boost~superlu-dist+superlu+hdf5+zlib+pnetcdf@master')
 
-    def build_type(self):
-        if '+debug' in self.spec:
-            return 'Debug'
-        else:
-            return 'Release'
-
     def cmake_args(self):
         spec = self.spec
         options = []