Hadrian: override $(ghc-config-mk), to prevent redundant config generation

This required making the 'ghc-config-mk' variable overridable in
testsuite/mk/boilerplate.mk, and then making use of this in hadrian
to point to '<build root>/test/ghcconfig' instead, which is where we
always put the test config.

Previously, we would build ghc-config and run it against the
GHC to be tested, a second time, while we're running the tests, because some
include testsuite/mk/boilerplate.mk. This was causing unexpected output
failures.

1 files changed, 8 insertions, 0 deletions

diff --git a/hadrian/src/Rules/Test.hs b/hadrian/src/Rules/Test.hs
index f7e5c45051..6a010df45a 100644
--- a/hadrian/src/Rules/Test.hs
+++ b/hadrian/src/Rules/Test.hs
@@ -107,6 +107,9 @@ testRules = do
         --       Shake can keep track of them, but it is not as easy as it seems
         --       to get that to work.
         liftIO $ do
+            -- Many of those env vars are used by Makefiles in the
+            -- test infrastructure, or from tests or their
+            -- Makefiles.
             setEnv "MAKE" makePath
             setEnv "PYTHON" pythonPath
             setEnv "TEST_HC" ghcPath
@@ -116,6 +119,11 @@ testRules = do
             setEnv "CHECK_API_ANNOTATIONS"
                    (top -/- root -/- checkApiAnnotationsProgPath)
 
+            -- This lets us bypass the need to generate a config
+            -- through Make, which happens in testsuite/mk/boilerplate.mk
+            -- which is in turn included by all test 'Makefile's.
+            setEnv "ghc-config-mk" (top -/- root -/- ghcConfigPath)
+
         -- Execute the test target.
         -- We override the verbosity setting to make sure the user can see
         -- the test output: https://gitlab.haskell.org/ghc/ghc/issues/15951.