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/hpx/package.py

@@ -40,10 +40,3 @@ class Hpx(CMakePackage):
     def cmake_args(self):
         args = ['-DHPX_BUILD_EXAMPLES=OFF', '-DHPX_MALLOC=system']
         return args
-
-    def build_type(self):
-        spec = self.spec
-        if '+debug' in spec:
-            return 'Debug'
-        else:
-            return 'Release'