Add wscript for checkout via waf

* We depend on spack@visionary

Depends-On: 15477
Change-Id: I397d39cf4f39fda02fe10724a23b00de94f41086

wscript

+def depends(ctx):
+    ctx("spack", branch="visionary")
+
+def options(opt):
+    pass
+
+def configure(cfg):
+    pass
+
+def build(bld):
+    pass