Merge "envsetup.sh: don't assume 'cd' is builtin"

    cached_vars=`cat $T/build/envsetup.sh | tr '()' '  ' | awk '{for(i=1;i<=NF;i++) if($i~/get_build_var/) print $(i+1)}' | sort -u | tr '\n' ' '`

    cached_abs_vars=`cat $T/build/envsetup.sh | tr '()' '  ' | awk '{for(i=1;i<=NF;i++) if($i~/get_abs_build_var/) print $(i+1)}' | sort -u | tr '\n' ' '`

    # Call the build system to dump the "<val>=<value>" pairs as a shell script.

    build_dicts_script=`\cd $T; build/soong/soong_ui.bash --dumpvars-mode \

    build_dicts_script=`\builtin cd $T; build/soong/soong_ui.bash --dumpvars-mode \

                        --vars="$cached_vars" \

                        --abs-vars="$cached_abs_vars" \

                        --var-prefix=var_cache_ \