I'm trying to build my own custom Linux system using the BLFS and LFS books as well as a lot of external resources. I would really like to run KDE4 on my system, but I simply cannot get kdebindings-4.6.4 to compile....

[ 53%] Built target smokeokular
Linking CXX shared library ../../../lib/libqtruby4shared.so
/usr/lib/gcc/i686-pc-linux-gnu/4.5.3/../../../libruby-static.a(sprintf.: In function `rb_str_catf':
/sources/kde/ruby-1.9.2-p180/newruby2/ruby/sprintf.c:1236: multiple definition of `rb_str_catf'
CMakeFiles/qtruby4shared.dir/Qt.o:/sources/kde/kdebindings-4.6.4/ruby/qtruby/src/Qt.cpp:479: first defined here
/usr/lib/gcc/i686-pc-linux-gnu/4.5.3/../../../libruby-static.a(string.: In function `rb_str_crypt':
/sources/kde/ruby-1.9.2-p180/newruby2/ruby/string.c:6766: undefined reference to `crypt'
/usr/lib/gcc/i686-pc-linux-gnu/4.5.3/../../../libruby-static.a(time.: In function `time_init_0':
/sources/kde/ruby-1.9.2-p180/newruby2/ruby/time.c:1940: undefined reference to `clock_gettime'
/usr/lib/gcc/i686-pc-linux-gnu/4.5.3/../../../libruby-static.a(thread.: In function `timeofday':
/sources/kde/ruby-1.9.2-p180/newruby2/ruby/thread.c:931: undefined reference to `clock_gettime'
/sources/kde/ruby-1.9.2-p180/newruby2/ruby/thread.c:931: undefined reference to `clock_gettime'
/usr/lib/gcc/i686-pc-linux-gnu/4.5.3/../../../libruby-static.a(thread.: In function `native_cond_timeout':
/sources/kde/ruby-1.9.2-p180/newruby2/ruby/thread_pthread.c:336: undefined reference to `clock_gettime'
/sources/kde/ruby-1.9.2-p180/newruby2/ruby/thread_pthread.c:336: undefined reference to `clock_gettime'
/usr/lib/gcc/i686-pc-linux-gnu/4.5.3/../../../libruby-static.a(thread.:/sources/kde/ruby-1.9.2-p180/newruby2/ruby/thread_pthread.c:336: more undefined references to `clock_gettime' follow
collect2: ld returned 1 exit status
make[2]: *** [lib/libqtruby4shared.so.2.0.0] Error 1
make[1]: *** [ruby/qtruby/src/CMakeFiles/qtruby4shared.dir/all] Error 2
make: *** [all] Error 2

Any help would be greatly appreciated =)

Have you checked that you are using a version of Ruby which is targeted by the KDE Ruby bindings?