Makefile: Use PYTHONPATH to find python sources

Use PYTHONPATH to let python find python sources in the source dir.

Author: vries

Makefile

@@ -138,7 +138,7 @@ plugin: autogenerated-config.h $(PLUGIN_DSO)
 # When running the plugin from a working copy, use LD_LIBARY_PATH=gcc-c-api
 # so that the plugin can find its libgcc-c-api.so there
 #
-INVOCATION_ENV_VARS := CC_FOR_CPYCHECKER=$(CC) LD_LIBRARY_PATH=gcc-c-api:$(LD_LIBRARY_PATH) CC=$(CC)
+INVOCATION_ENV_VARS := PYTHONPATH=$(srcdir)./ CC_FOR_CPYCHECKER=$(CC) LD_LIBRARY_PATH=gcc-c-api:$(LD_LIBRARY_PATH) CC=$(CC)
 
 # When installing, both the plugin and libgcc-c-api.so will be installed to
 # $(GCCPLUGINS_DIR), so we give the plugin an RPATH of $(GCCPLUGINS_DIR)
@@ -199,7 +199,7 @@ $(PLUGIN_GENERATED_SOURCE_FILES): autogenerated-%.c: generate-%-c.py $(GENERATOR
 	$(PYTHON) $< > $@
 
 autogenerated-casts.c:  autogenerated-gimple-types.txt autogenerated-tree-types.txt autogenerated-rtl-types.txt generate-casts-c.py
-	$(PYTHON) $(srcdir)generate-casts-c.py autogenerated-casts.c autogenerated-casts.h $(xmldir)
+	PYTHONPATH=$(srcdir)./gcc-c-api	$(PYTHON) $(srcdir)generate-casts-c.py autogenerated-casts.c autogenerated-casts.h $(xmldir)
 
 autogenerated-gimple.c: autogenerated-gimple-types.txt autogenerated-tree-types.txt autogenerated-rtl-types.txt maketreetypes.py
 autogenerated-tree.c: autogenerated-tree-types.txt maketreetypes.py