configure.in vs. configure.ac clash

[Guido Draheim]

while trying to create an rpm for the mp4h project, I jumped on the
following problem:

- the toplevel configure has configure.ac
- a subdir libltdl/ is copied in, which contains a configure.in
- the rpm macro %configure will expand to a line like
   CFLAGS=$RPM_CFLAGS configure --prefix ....
- the toplevel configure will call the the ltdl/configure using...
   configure sometarget --prefix... 'CFLAGS=$expanded_RPM_CFLAGS'

and BOOM. 
Yepp, I can fix it while *not* using %configure with the extra CFLAGS settings.
Anyway, interesting to see ;-) .. have fun, guido

P.S. here are the last lines:

config.status: creating config.h
configure: configuring in libltdl
configure: running /bin/sh './configure'  i586-mandrake-linux-gnu --prefix=/usr 
--exec-prefix=/usr --bindir=/usr/bin
--sbindir=/usr/sbin --sysconfdir=/etc --datadir=/usr/share 
--includedir=/usr/include --libdir=/usr/lib --libexecdir=/usr/lib
--localstatedir=/var/lib --sharedstatedir=/usr/com --mandir=/usr/share/man 
--infodir=/usr/share/info --with-modules 'CFLAGS=-O3
-fomit-frame-pointer -pipe -mcpu=pentiumpro -march=i586 -ffast-math 
-fno-strength-reduce' build_alias=i586-mandrake-linux-gnu
host_alias=i586-mandrake-linux-gnu target_alias=i586-mandrake-linux-gnu 
--enable-ltdl-convenience --cache-file=/dev/null
--srcdir=.
configure: warning: CFLAGS=-O3 -fomit-frame-pointer -pipe -mcpu=pentiumpro 
-march=i586 -ffast-math -fno-strength-reduce: invalid
host type
configure: error: can only configure for one host and one target at a time
configure: error: /bin/sh './configure' failed for libltdl
sed: can't read confdefs.h: No such file or directory
Fehler: Bad exit status from /my/rpm/tmp/rpm-tmp.16825 (%build)