[build] Fix Makefile based 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 430 matching lines @@
 clean: $(addsuffix .clean, $(ARCHES) $(ANDROID_ARCHES) $(NACL_ARCHES)) native.clean gtags.clean tags.clean
 
 # GYP file generation targets.
 OUT_MAKEFILES = $(addprefix $(OUTDIR)/Makefile.,$(BUILDS))
 $(OUT_MAKEFILES): $(GYPFILES) $(ENVFILE)
         $(eval CXX_TARGET_ARCH:=$(shell $(CXX) -v 2>&1 | grep ^Target: | \
                 cut -f 2 -d " " | cut -f 1 -d "-" ))
         $(eval CXX_TARGET_ARCH:=$(subst aarch64,arm64,$(CXX_TARGET_ARCH)))
         $(eval CXX_TARGET_ARCH:=$(subst x86_64,x64,$(CXX_TARGET_ARCH)))
         $(eval V8_TARGET_ARCH:=$(subst .,,$(suffix $(basename $@))))
-        PYTHONPATH="$(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=. \
                       -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)
@@ skipping 52 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)