[hadrian] Rebuild programs on dynamicGhcPrograms/ghcProfiled change

Currently, if you change these ^ flavour parameters, rebuilding is not
triggered, since `programContext` doesn't set up a dependency on
those values.

Exposing these values via an oracle does set the dependency and
properly triggers a rebuild of binaries.

Several attempts to factor out these actions ended up in cyclic
dependency here or there. I'm not absolutely happy with this variant
either, but at least it works.

====

Issue repro:

In UserSettings.hs:
```
dbgDynamic = defaultFlavour { name = "dbg-dynamic"
                            , dynamicGhcPrograms = pure True,
                            ... }

dbgStatic = defaultFlavour { name = "dbg-static"
                           , dynamicGhcPrograms = pure False
                           ... }
```

Then in console:

```
$ hadrian/build.sh -j --flavour=dbg-dynamic
... does the build
$ hadrian/build.sh -j --flavour=dbg-static
... does nothing, considers binaries up to date
```

1 files changed, 1 insertions, 18 deletions

diff --git a/hadrian/src/Settings.hs b/hadrian/src/Settings.hs
index 0548bccfae..ba0cff770a 100755
--- a/hadrian/src/Settings.hs
+++ b/hadrian/src/Settings.hs
@@ -1,8 +1,7 @@
 module Settings (
     getArgs, getLibraryWays, getRtsWays, flavour, knownPackages,
     findPackageByName, unsafeFindPackageByName, unsafeFindPackageByPath,
-    isLibrary, stagePackages, programContext, getIntegerPackage,
-    completeSetting
+    isLibrary, stagePackages, getIntegerPackage, completeSetting
     ) where
 
 import CommandLine
@@ -68,22 +67,6 @@ flavour = do
 getIntegerPackage :: Expr Package
 getIntegerPackage = expr (integerLibrary =<< flavour)
 
--- TODO: there is duplication and inconsistency between this and
--- Rules.Program.getProgramContexts. There should only be one way to get a
--- context / contexts for a given stage and package.
-programContext :: Stage -> Package -> Action Context
-programContext stage pkg = do
-    profiled <- ghcProfiled <$> flavour
-    dynGhcProgs <- dynamicGhcPrograms =<< flavour
-    return $ Context stage pkg (wayFor profiled dynGhcProgs)
-
-    where wayFor prof dyn
-            | prof && dyn                          =
-                error "programContext: profiling+dynamic not supported"
-            | pkg == ghc && prof && stage > Stage0 = profiling
-            | dyn && stage > Stage0                = dynamic
-            | otherwise                            = vanilla
-
 -- TODO: switch to Set Package as the order of packages should not matter?
 -- Otherwise we have to keep remembering to sort packages from time to time.
 knownPackages :: [Package]