WINCETARGETFILES=BootImage，used in sources file,This macro definition specifies nonstandard target files that Build.exe should build after Build.exe links all other targets in the current directory.If this macro definition is present, custom rules that you define in Makefile.inc, which is an optional file that can exist in the same directory as a sources file, are also applied.
Wince在查找库文件时会到_PLATCOMMONLIB=$(_PLATFORMROOT)\common\lib中找，查看sources.cmn可知。