Fix compilation of cmm files with -outputdir (Trac #9050)

compiler/main/CodeOutput.lhs

@@ -192,11 +192,8 @@ outputForeignStubs dflags mod location stubs
    stub_c <- newTempName dflags "c"
 
    case stubs of
-     NoStubs -> do
-        -- When compiling External Core files, may need to use stub
-        -- files from a previous compilation
-        stub_h_exists <- doesFileExist stub_h
-        return (stub_h_exists, Nothing)
+     NoStubs ->
+        return (False, Nothing)
 
      ForeignStubs h_code c_code -> do
         let

testsuite/tests/driver/T9050.cmm

+// empty

testsuite/tests/driver/all.T

@@ -395,3 +395,7 @@ test('T2507',
 test('T703', normal, run_command, ['$MAKE -s --no-print-directory T703'])
 test('T8101', normal, compile, ['-Wall -fno-code'])
 
+def build_T9050(name, way):
+     return simple_build(name + '.cmm', way, '-outputdir=. ', 0, '', 0, 0, 0)
+test('T9050', normal, build_T9050, [])
+