Thread: can't compile glib

i have installed gettext in /opt/gtk，
./configure --prefix=/opt/gtk
make
make install
1.why pkg-config --modversion gettext can't find it?
root@ocean:~# pkg-config --modversion gettext
Package gettext was not found in the pkg-config search path.
Perhaps you should add the directory containing `gettext.pc'
to the PKG_CONFIG_PATH environment variable
No package 'gettext' found

2.when i install glib，
./configure --prefix=/opt/gtk
the output ，
checking for msgfmt... no
configure: error:
You must have either have gettext support in your C library, or use the
GNU gettext library. (gettext - GNU Project - Free Software Foundation (FSF)
how to solve it ？