[build] Fix Makefile based (native) build.

Makefile

 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 441 matching lines @@
         GYP_GENERATORS=make \
         tools/gyp/gyp --generator-output="$(OUTDIR)" gypfiles/all.gyp \
                       -Igypfiles/standalone.gypi --depth=. \
                       -Dv8_target_arch=$(V8_TARGET_ARCH) \
                       $(if $(findstring $(CXX_TARGET_ARCH),$(V8_TARGET_ARCH)), \
                       -Dtarget_arch=$(V8_TARGET_ARCH),) \
                       $(if $(findstring optdebug,$@),-Dv8_optimized_debug=1,) \
                       -S$(suffix $(basename $@))$(suffix $@) $(GYPFLAGS)
 
 $(OUTDIR)/Makefile.native: $(GYPFILES) $(ENVFILE)
-        PYTHONPATH="$(shell pwd)/tools/generate_shim_headers:$(shell pwd)/build:$(PYTHONPATH):$(shell pwd)/tools/gyp/pylib:$(PYTHONPATH)" \
+        PYTHONPATH="$(shell pwd)/tools/generate_shim_headers:$(shell pwd)/gypfiles:$(PYTHONPATH):$(shell pwd)/tools/gyp/pylib:$(PYTHONPATH)" \
         GYP_GENERATORS=make \
         tools/gyp/gyp --generator-output="$(OUTDIR)" gypfiles/all.gyp \
                       -Igypfiles/standalone.gypi --depth=. -S.native $(GYPFLAGS)
 
 # Note that NACL_SDK_ROOT must be set to point to an appropriate
 # Native Client SDK before using this makefile. You can download
 # an SDK here:
 #   https://developers.google.com/native-client/sdk/download
 # The path indicated by NACL_SDK_ROOT will typically end with
 # a folder for a pepper version such as "pepper_25" that should
@@ skipping 41 matching lines @@
 tags: gtags.files $(wildcard $(shell cat gtags.files 2> /dev/null))
         @(ctags --version | grep 'Exuberant Ctags' >/dev/null) || \
                 (echo "Please install Exuberant Ctags (check 'ctags --version')" >&2; false)
         ctags --fields=+l -L $<
 
 tags.clean:
         rm -r tags
 
 dependencies builddeps:
         $(error Use 'gclient sync' instead)