I've compiled the metamod version myself without the need for this specific stdc++ library.
Code:
> ldd joebot_mm_i386.so
libstdc++.so.5 => /usr/lib/libstdc++.so.5 (0x40176000)
libdl.so.2 => /lib/tls/libdl.so.2 (0x4022e000)
libc.so.6 => /lib/tls/libc.so.6 (0x40231000)
libm.so.6 => /lib/tls/libm.so.6 (0x4036a000)
libgcc_s.so.1 => /lib/libgcc_s.so.1 (0x4038d000)
/lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x80000000)