Adding SDL to a configure script

I am running Gentoo Linux and am attempting to add the SDL cflags and
libraries to a configure script. I’ve followed the instructions here:

I rerun aclocal,automake,autoconf then configure which produces:

checking for SDL - version >= 1.2.0… no
*** Could not run SDL test program, checking why…
*** The test program failed to compile or link. See the file config.log
for the
*** exact error that occured. This usually means SDL was incorrectly
*** or that you have moved SDL since it was installed. In the latter
case, you
*** may want to edit the sdl-config script: /usr/bin/sdl-config
configure: error: *** SDL version 1.2.0 not found!

Looking at the config.log I get the following:

onfigure:9546: checking for sdl-config
configure:9564: found /usr/bin/sdl-config
configure:9577: result: /usr/bin/sdl-config
configure:9585: checking for SDL - version >= 1.2.0
configure:9676: g++ -o conftest -g -O2 -L/usr/lib
-Wl,-rpath,/usr/lib -lSDL -lpthread >&5
configure:9637:17: SDL.h: No such file or directory
configure:9679: $? = 1
configure: program exited with status 1

It appears to not be picking up the CFLAGS from sdl-config --cflags even
though looking at aclocal.m4 and it appears to call the
above statement.

sdl-config --cflags returns this when I run it on the commandline:

-I/usr/include/SDL -D_REENTRANT

I am quite perplexed. The automake/autoconf files were original
generated by kdevelop 3.0 and I modified them to include what was in the

Any help is greatly appreciated.