Hacking in the .pp suffix rule: leave #include directives in place.
#-----------------------------------------------------------------------------
# Preprocessor suffix rule
#-----------------------------------------------------------------------------
# Preprocessor suffix rule
+# We're careful to remove cpp-droppings from the generated file; things like
+# '#line' pragmas. But we also leave in #include directives, because these
+# are likely to be intentional (perhaps the file is going to be CPP'd again -
+# this is used by ghc/compiler/parser/Parser.y.pp).
+
- $(CPP) $(RAWCPP_FLAGS) $(CPP_OPTS) -x c $< | $(SED) -e '/^#/d' > $@
+ $(CPP) $(RAWCPP_FLAGS) $(CPP_OPTS) -x c $< | $(SED) -e '/^#[^i]/d' > $@