Btw. I'm using autoconf-2.13, so it should be compliant with the build-cfg script.

Next, even if I set the define the ac_version to bypass the guessing code, build-cfg fails.

bash-4.1# ac_version=2.13 make
AR_HOST=' /usr/qnx650/host/qnx6/x86/usr/bin/cc -a' AS_HOST=' /usr/qnx650/host/qnx6/x86/usr/bin/cc -c' CC_HOST=' /usr/
qnx650/host/qnx6/x86/usr/bin/cc -c' CL_HOST=' /usr/qnx650/host/qnx6/x86/usr/bin/cc' CP_HOST='/bin/cp -vfpc ' DATE_HOST='
/usr/bin/date +%Y/%m/%d-%T-%Z' ECHO_HOST='/bin/echo' FL_HOST='/usr/qnx650/target/qnx6/usr/include/mk/flist-unix' 
HOST_HOST='/bin/hostname' INSTALL_ROOT_AR='/usr/qnx650/target/qnx6/x86' INSTALL_ROOT_ARSHR='/usr/qnx650/target/qnx6/x86'
 INSTALL_ROOT_DLL='/usr/qnx650/target/qnx6/x86' INSTALL_ROOT_EX='/usr/qnx650/target/qnx6/x86' INSTALL_ROOT_HDR='/usr/
qnx650/target/qnx6/usr/include' INSTALL_ROOT_SO='/usr/qnx650/target/qnx6/x86' INSTALL_ROOT_mingw32='/usr/mingw32' 
INSTALL_ROOT_nto='/usr/qnx650/target/qnx6' INSTALL_ROOT_qnx4='/usr/qnx4' INSTALL_ROOT_solaris='/opt/QNXsdk/target/
solaris' INSTALL_ROOT_win32='/usr/win32' KSH_HOST='/usr/qnx650/host/qnx6/x86/usr/bin/ksh' LD_HOST=' /usr/qnx650/host/
qnx6/x86/usr/bin/cc' LN_HOST='/bin/ln -sf ' MG_HOST='/bin/true' MKASMOFF_HOST='/usr/bin/mkasmoff ' MP_HOST='/usr/qnx650/
target/qnx6/usr/include/mk/makepriv-qnx' PB_HOST='/usr/qnx650/host/qnx6/x86/usr/bin/phabbind' PINFO_DATE='2011/03/29-06:
24:50-EST' PINFO_HOST='footrest3' PINFO_STATE='Experimental' PINFO_TAGID='' PINFO_USER='root' PWD_HOST='/bin/pwd' 
QNX_HOST='/usr/qnx650/host/qnx6/x86' RM_HOST='/bin/rm -f ' SYSNAME='nto' TOUCH_HOST='/usr/bin/touch' UM_HOST='/usr/
qnx650/host/qnx6/x86/usr/bin/usemsg' USER_HOST='/usr/bin/id -un' QNXVFLAGS='' QNXROOTINCS='-I/usr/qnx650/target/qnx6/usr
/include' QNXROOTLIBS='-L/usr/qnx650/target/qnx6/x86/lib -L/usr/qnx650/target/qnx6/x86/usr/lib' /usr/qnx650/host/qnx6/
x86/usr/bin/ksh /usr/qnx650/target/qnx6/usr/include/mk/build-cfg 
*** Can only configure for one host and one target at a time.
*** Can only configure for one host and one target at a time.
*** Can only configure for one host and one target at a time.
*** Can only configure for one host and one target at a time.
*** Can only configure for one host and one target at a time.
*** Can only configure for one host and one target at a time.
*** Can only configure for one host and one target at a time.
*** Can only configure for one host and one target at a time.
Usage: configure [OPTIONS] [HOST]

Options: [defaults in brackets]
 --prefix=MYDIR		 install into MYDIR [/usr/local]
 --exec-prefix=MYDIR	 install host-dependent files into MYDIR [/usr/local]
 --help			 print this message [normal config]
 --build=BUILD		 configure for building on BUILD [BUILD=HOST]
[...]