Allow a relativ path to the NaCl SDK when building

Makefile.nacl

 #
 # Copyright 2013 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
@@ skipping 28 matching lines @@
 ifeq ($(HOST_OS), linux)
   TOOLCHAIN_DIR = linux_x86_glibc
 else
   ifeq ($(HOST_OS), mac)
     TOOLCHAIN_DIR = mac_x86_glibc
   else
     $(error Host platform "${HOST_OS}" is not supported)
   endif
 endif
 
-TOOLCHAIN_PATH = ${NACL_SDK_ROOT}/toolchain
+TOOLCHAIN_PATH = $(realpath ${NACL_SDK_ROOT}/toolchain)
 NACL_TOOLCHAIN ?= ${TOOLCHAIN_PATH}/${TOOLCHAIN_DIR}
 
 ifeq ($(ARCH), nacl_ia32)
   GYPENV = nacl_target_arch=nacl_ia32 v8_target_arch=arm v8_host_arch=ia32
   TOOLCHAIN_ARCH = x86-4.4
   NACL_CC = "$(NACL_TOOLCHAIN)/bin/i686-nacl-gcc"
   NACL_CXX = "$(NACL_TOOLCHAIN)/bin/i686-nacl-g++"
   NACL_LINK = "$(NACL_TOOLCHAIN)/bin/i686-nacl-g++"
 else
   ifeq ($(ARCH), nacl_x64)
@@ skipping 27 matching lines @@
 
 # NACL GYP file generation targets.
 $(NACL_MAKEFILES):
         @GYP_GENERATORS=make \
         GYP_DEFINES="${GYPENV}" \
         CC=${NACL_CC} \
         CXX=${NACL_CXX} \
         build/gyp/gyp --generator-output="${OUTDIR}" build/all.gyp \
                       -Ibuild/standalone.gypi --depth=. \
                       -S.$(subst .,,$(suffix $@)) $(GYPFLAGS)