[yocto] How to add libraries to poky toolchain

[Matthew Clark]

I'm trying to cross build a package with a configure script and I'm
running into a problem because it can't find a missing library
dependency:

arm-poky-linux-gnueabi-gcc  -march=armv7-a -mfloat-abi=hard -mfpu=neon
-mtune=cortex-a8
--sysroot=/opt/poky/1.8/sysroots/cortexa8hf-vfp-neon-poky-linux-gnueabi
-o conftest
-O2 -pipe -g -feliminate-unused-debug-types  -Wl,-O1 -Wl,--hash-style=gnu
-Wl,--as-needed myconftest.c -lgdbm

/opt/poky/1.8/sysroots/x86_64-pokysdk-linux/usr/libexec/arm-poky-linux-gnueabi/gcc/arm-poky-linux-gnueabi/4.9.2/ld:
cannot find -lgdbm
collect2: error: ld returned 1 exit status

A quick look shows there's no libgdbm in
/opt/poky/1.8/sysroots/cortexa8hf-vfp-neon-poky-linux-gnueabi folder,
though it is in
/opt/poky/1.8/sysroots/x86_64-pokysdk-linux (which, of course, is for
86_64, not ARM)

I'd bitbaked the meta-toolchain and installed the .sh file, but
apparently I need to add more libraries.  What's the best way to do
that?  Is there an additional package I need to bitbake?   I can
kludge it myself, by manually copying stuff into
/opt/poky/1.8/sysroots/cortexa8hf-vfp-neon-poky-linux-gnueabi but I'd
much rather have something more elegant so I can replicate it to other
development machines.

Thanks.

Matt