Can't add Lex/Par to autogen-modules in BNFC.cabal

These modules should not be shipped but be generated by `alex` and
`happy` **on the target system**.

However, if we add them to `autogen-modules` even the `Lex.x/Par.y` will
not be shipped with `cabal sdist`.

Solution is to make sure that there is no `Lex/Par.hs` along `Lex.x/Par.y`
when invoking `cabal sdist`.  This is embodied in new goal `make sdist`.

source/BNFC.cabal

@@ -155,6 +155,14 @@ library
   --   BNFC.Lex
   --   -- Generated by happy
   --   BNFC.Par
+  -- 2023-11-03 We cannot add BNFC.{Lex,Par} as then the Lex.x and Par.y files
+  -- are not bundled by cabal dist.
+  -- Just make sure that there is no src/BNFC/{Lex,Par}.hs before running cabal sdist,
+  -- otherwise we will end up with both Lex.hs and Lex.x (resp. Par.{hs,y})
+  -- which will cause alex/happy to not be run, leading to build failures.
+  autogen-modules:
+    -- Generated by cabal
+    Paths_BNFC
   other-modules:
     -- Generated by cabal
     Paths_BNFC

source/Makefile

@@ -62,6 +62,15 @@ TAGS :
 # Binary package (tgz, for linux)
 bdist: dist/${BDIST_TAG}.tar.gz
 
+# Source package
+# Andreas, 2023-11-03, PR #466: need to remove BNFC/{Lex,Par}.hs,
+# otherwise they will be shipped in the sdist package
+# and cause compilation to fail.
+sdist:
+	make -C src clean
+	cabal sdist
+
+# OLD goal
 dist/%.tar.gz:
 	cabal v1-clean
 	cabal v1-install ${CABAL_OPTS} --only-dependencies

source/src/Makefile

@@ -62,4 +62,8 @@ fake-cabal :
 rm-fake-cabal :
 	rm inferior-haskell-find-project-root.cabal
 
+.PHONY: clean
+clean :
+	rm BNFC/Lex.hs BNFC/Par.hs BNFC/*.bak
+
 #EOF