problem with building kdemultimedia RPM package for mp3 support

I'm using fedora 7, 64-bit edition. I'm trying to add the mp3 support for xine. I'm using for this purpose the packages kdemultimedia-3.5.6-7.fc7.src.rpm and kdemultimedia-3.5.6.tar.bz2. I tweaked the file /usr/src/redhat/SPECS/kdemultimedia.spec a little to enable mp3. I'm rebuilding a binary RPM package for kdemultimedia using the command:

The building process goes fine until I get the following error:

.libs/xinePlayObject_impl.o: In function `xine_shared_init':
/usr/src/redhat/BUILD/kdemultimedia-3.5.6-patched/xine_artsplugin/xinePlayObject_impl.cpp:113: undefined reference to `pthread_create'

I get this error along with some other errors all related to pthread. The last command in the build process that preceded this error was

/bin/sh ../libtool --silent --mode=link --tag=CXX g++  -DNDEBUG -DNO_DEBUG -O2 -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic -fno-exceptions -fno-check-new -fno-common -DQT_CLEAN_NAMESPACE -DQT_NO_ASCII_CAST -DQT_NO_STL -DQT_NO_COMPAT -DQT_NO_TRANSLATION    -o libarts_xine.la -rpath /usr/lib64 -L/usr/lib64/qt-3.3/lib -L/usr/lib64 -Wl,--as-needed -Wl,--enable-new-dtags  -module -no-undefined -Wl,--no-undefined -Wl,--allow-shlib-undefined -pthread xinePlayObject.lo xinePlayObject_impl.lo audio_fifo_out.lo -L/usr/lib64 -lxine   -lX11  -lXext -lkmedia2_idl -lsoundserver_idl -lartsflow

As I see the -pthread option is specified in this command(and the pthread library is installed on my system for sure), so it's most probably not a linking problem. May it be a missing header file in the source file /usr/src/redhat/BUILD/kdemultimedia-3.5.6-patched/xine_artsplugin/xinePlayObject_impl.cpp? Does anyone have an idea how to overcome this error?