When i do:
./configure --prefix=/opt/twinkle --without-zrtp --without-kde
--disable-fast-perl --with-extra-includes=/opt/twinkle/include/
--with-extra-libs=/opt/twinkle/lib/

I've already installed iLBC in the /opt/twinkle/include/ and /opt/twinkle/lib/,
But it seems that with-extra-includes and with-extra-libs is for KDE only.

Work around:
export LDFLAGS=-L/opt/twinkle/lib
export CXXFLAGS=-I/opt/twinkle/include

Then it works.