换了msys2后，编译xerces-c-2.8.0，./runConfigure -pmingw-msys -cgcc -xg++ -s -P/opt/xercesc-2.8.0 后遇到如标题所示问题，详下：

checking for unistd.h... yes
checking for XMLByte... no
checking build system type... ./config.guess: unable to guess system type

This script, last modified 2002-07-09, has failed to recognize
the operating system you are using. It is advised that you
download the most up to date version of the config scripts from

    ftp://ftp.gnu.org/pub/gnu/config/

If the version you run (./config.guess) is already up to date, please
send the following data and any information you think might be
pertinent to <config-patches@gnu.org> in order to provide the needed
information to handle your system.

config.guess timestamp = 2002-07-09

uname -m = x86_64
uname -r = 2.0.0(0.280/5/3)
uname -s = MINGW64_NT-6.1
uname -v = 2014-11-06 20:34

/usr/bin/uname -p = unknown
/bin/uname -X     =

hostinfo               =
/bin/universe          =
/usr/bin/arch -k       =
/bin/arch              = x86_64
/usr/bin/oslevel       =
/usr/convex/getsysinfo =

UNAME_MACHINE = x86_64
UNAME_RELEASE = 2.0.0(0.280/5/3)
UNAME_SYSTEM  = MINGW64_NT-6.1
UNAME_VERSION = 2014-11-06 20:34
configure: error: cannot guess build type; you must specify one

google也说是config.guess比较旧，msys环境编译没有问题，去mingw-w64的svn上拉了个config.guess下来替换掉后问题解决：

checking for stdint.h... yes
checking for unistd.h... yes
checking for XMLByte... no
checking build system type... x86_64-pc-mingw32
checking host system type... x86_64-pc-mingw32
configure: creating ./config.status
config.status: creating Makefile

configure:cannot guess build type; you must specify one