hadrian/tool-args: Write output to intermediate file rather than via stdout

This allows us to see the output of hadrian while it is doing the setup.

hadrian/ghci-cabal.in

@@ -3,7 +3,8 @@
 # This file is generated by configure from ghci-cabal.in
 
 set -e
-
+export TOOL_OUTPUT=.hadrian_ghci/ghci_args
 # Replace newlines with spaces, as these otherwise break the ghci invocation on windows.
-GHC_FLAGS="$GHC_FLAGS $(TERM=dumb CABFLAGS=-v0 "hadrian/build-cabal" tool:ghc/Main.hs -q --build-root=.hadrian_ghci --flavour=ghc-in-ghci $HADRIAN_ARGS | tr '\n\r' ' ')"
+CABFLAGS=-v0 "hadrian/build-cabal" tool:compiler/GHC.hs --build-root=.hadrian_ghci --flavour=ghc-in-ghci $HADRIAN_ARGS
+GHC_FLAGS="$GHC_FLAGS $(cat $TOOL_OUTPUT | tr '\n\r' ' ')"
 @WithGhc@ --interactive $GHC_FLAGS $@ -fno-code -fwrite-interface -hidir=.hadrian_ghci/interface -O0 +RTS -A128m

hadrian/ghci-stack.in

@@ -4,6 +4,9 @@
 
 set -e
 
+export TOOL_OUTPUT=.hadrian_ghci/ghci_args
+TERM=dumb CABFLAGS=-v0 "hadrian/build-cabal" tool:compiler/GHC.hs -q --build-root=.hadrian_ghci --flavour=ghc-in-ghci $HADRIAN_ARGS
+
 # Replace newlines with spaces, as these otherwise break the ghci invocation on windows.
-GHC_FLAGS="$GHC_FLAGS $(TERM=dumb CABFLAGS=-v0 "hadrian/build-stack" tool-args -q --build-root=.hadrian_ghci --flavour=ghc-in-ghci $HADRIAN_ARGS | tr '\n\r' ' ')"
+GHC_FLAGS="$GHC_FLAGS $(cat $TOOL_OUTPUT | tr '\n\r' ' ')"
 stack exec -- @WithGhc@ --interactive $GHC_FLAGS "$@" -fno-code -fwrite-interface -hidir=.hadrian_ghci/interface -O0 +RTS -A128m

hadrian/hie-bios

@@ -3,5 +3,5 @@
 # When run, this program will output a list of arguments which are necessary to
 # load the GHC library component into GHCi. The program is used by `ghcide` in
 # order to automatically set up the correct GHC API session for a project.
-TERM=dumb CABFLAGS=-v0 $PWD/hadrian/build-cabal tool:$1 -q --build-root=.hie-bios --flavour=ghc-in-ghci > $HIE_BIOS_OUTPUT
+TERM=dumb CABFLAGS=-v0 TOOL_OUTPUT=$HIE_BIOS_OUTPUT $PWD/hadrian/build-cabal tool:$1 -q --build-root=.hie-bios --flavour=ghc-in-ghci
 

hadrian/hie-bios.bat

 set TERM=dumb
 set CABFLAGS=-v0
-%CD%\hadrian\build-cabal.bat tool:%1 -q --build-root=_hie-bios --flavour=ghc-in-ghci > %HIE_BIOS_OUTPUT%
+set TOOL_OUTPUT=%HIE_BIOS_OUTPUT%
+%CD%\hadrian\build-cabal.bat tool:%1 --build-root=_hie-bios --flavour=ghc-in-ghci

hadrian/src/Rules/ToolArgs.hs

@@ -12,6 +12,7 @@ import Settings
 import Hadrian.Oracles.Cabal
 import Hadrian.Haskell.Cabal.Type
 import System.Directory (canonicalizePath)
+import System.Environment (lookupEnv)
 
 -- | @tool:@ is used by tooling in order to get the arguments necessary
 -- to set up a GHC API session which can compile modules from GHC. When
@@ -48,11 +49,15 @@ mkToolTarget :: [String] -> Package -> Action ()
 mkToolTarget es p = do
     -- This builds automatically generated dependencies. Not sure how to do
     -- this generically yet.
+    putProgressInfo ("Computing arguments for " ++ pkgName p)
     allDeps
     let fake_target = target (Context stage0InTree p (if windowsHost then vanilla else dynamic))
                         (Ghc ToolArgs stage0InTree) [] ["ignored"]
     arg_list <- interpret fake_target getArgs
-    liftIO $ putStrLn (intercalate "\n" (arg_list ++ es))
+    liftIO $ lookupEnv "TOOL_OUTPUT" >>= \case
+      Nothing -> putStrLn (intercalate "\n" (arg_list ++ es))
+      Just out -> writeFile out (intercalate "\n" (arg_list ++ es))
+
 allDeps :: Action ()
 allDeps = do
    do