DynFlags: don't store buildTag

`DynFlags.buildTag` was a field created from the set of Ways in
`DynFlags.ways`. It had to be kept in sync with `DynFlags.ways` which
was fragile. We want to avoid global state like this (#17957).

Moreover in #14335 we also want to support loading units with different
ways: target units would still use `DynFlags.ways` but plugins would use
`GHC.Driver.Ways.hostFullWays`. To avoid having to deal both with build
tag and with ways, we recompute the buildTag on-the-fly (should be
pretty cheap) and we remove `DynFlags.buildTag` field.

1 files changed, 1 insertions, 1 deletions

diff --git a/ghc/Main.hs b/ghc/Main.hs
index 14e2b8048c..541c07bdfa 100644
--- a/ghc/Main.hs
+++ b/ghc/Main.hs
@@ -198,7 +198,7 @@ main' postLoadMode dflags0 args flagWarnings = do
   let dflags4 = case lang of
                 HscInterpreted | not (gopt Opt_ExternalInterpreter dflags3) ->
                     let platform = targetPlatform dflags3
-                        dflags3a = updateWays $ dflags3 { ways = hostFullWays }
+                        dflags3a = dflags3 { ways = hostFullWays }
                         dflags3b = foldl gopt_set dflags3a
                                  $ concatMap (wayGeneralFlags platform)
                                              hostFullWays