libtool problem

[Parag N(पराग़)]

Hi,
   While mock building my package, i got errors at %install section as
libtool: install: `%RPM_BUILD_ROOT/usr/lib' must be an absolute directory name
Try `libtool --help --mode=install' for more information.
make[3]: *** [install-libLTLIBRARIES] Error 1

I know .la must not be specified in SPEC file but under %files section
i used all wild cards. The upstream tarball used libtool to install
.la files under /usr/bin. How can i solve this problem?
Regards,
Parag.