RTEMS Source Builder build error

[ruizx]

Hi all,
I try to build 4.11 rtems-powerpc cross compiler in Cygwin.
When compiling expat, the error occoured.

examples/.libs/lt-elements.c: In function 'main':
examples/.libs/lt-elements.c:315:3: warning: implicit declaration of function '_spawnv' [-Wimplicit-function-declaration]
examples/.libs/lt-elements.c:315:19: error: '_P_WAIT' undeclared (first use in this function)
examples/.libs/lt-elements.c:315:19: note: each undeclared identifier is reported only once for each function it appears in

The compile command is 
../source-builder/sb-set-builder --log=l-powerpc.txt --prefix=$HOME/development/rtems/4.11 4.11/rtems-powerpc

I find this mail form gnu described the same error, but the method is not usable.
http://lists.gnu.org/archive/html/libtool/2008-12/msg00056.html

Anyone meet this error? How to solve it?

Thanks & Best regards,
Rui Zhengxin