Testsuite: Bogus error with "_build/stage1/lib" not found

After rebasing a number (10-20) of tests now seem to fail with this bogus error:

=====> CallArity1(normal) 1 of 1 [0, 0, 0]
cd "/tmp/ghctest-kejzo99g/test   spaces/testsuite/tests/callarity/unittest/CallArity1.run" &&  "/home/andi/ghc_infer/_build/stage1/bin/ghc" -o CallArity1 CallArity1.hs -dcore-lint -dstg-lint -dcmm-lint -no-user-package-db -rtsopts -fno-warn-missed-specialisations -fshow-warning-groups -fdiagnostics-color=never -fno-diagnostics-show-caret -Werror=compat -dno-debug-output  -package ghc <
cd "/tmp/ghctest-kejzo99g/test   spaces/testsuite/tests/callarity/unittest/CallArity1.run" && ./CallArity1    "_build/stage1/lib"<
Wrong exit code for CallArity1(normal)(expected 0 , actual 1 )
Stderr ( CallArity1 ):
CallArity1: Missing file: _build/stage1/lib/settings
*** unexpected failure for CallArity1(normal)

I suspect the path or content of the argument "_build/stage1/lib" is wrong. Either it should be an absolute path or contain a setting from that file? Not completely sure.