cmake HAVE_CYGWIN_CONV_PATH examples

libarchive/libarchive CMakeLists.txt :1568 

CHECK_FUNCTION_EXISTS(cygwin_conv_path HAVE_CYGWIN_CONV_PATH)

alibaba/AliSQLBackup storage/innobase/xtrabackup/src/libarchive/CMakeLists.txt :531 

CHECK_SYMBOL_EXISTS(cygwin_conv_path "sys/cygwin.h" HAVE_CYGWIN_CONV_PATH)