I have the toolchain uncompressed in /opt, then in the Makefile I put something like this:
TOOLCHAIN = /opt/opendingux-toolchain
BINDIR = $(TOOLCHAIN)/usr/bin
CXX = $(BINDIR)/mipsel-linux-g++
Or you can add /opt/opendingux-toolchain/usr/bin to your PATH environment variable and ignore the TOOLCHAIN line. Also, I had to go in some folders of the toolchain to set the permissions of the executables because "make" couldn't execute them.
Then, for SDL you have to use sdl-config to get the available flags, but if you use only 'sdl-config --cflags' it runs the sdl-config file from your OS. What I had to do is this:
SDL_CFLAGS = `/opt/opendingux-toolchain/usr/bin/sdl-config --cflags`
SDL_LIBS = `/opt/opendingux-toolchain/usr/bin/sdl-config --libs`
That way it runs sdl-config from the toolchain and gets the correct flags. That solved my sound problem, hope it works.
Another option is opening "/opt/opendingux-toolchain/usr/bin/sdl-config" from the toolchain in a text editor and look there what's returning if "--cflags" or "--libs" is passed as a parameter, then you can just copy that in your Makefile instead, but it's not a good practice.
Anyway, it sounded like you mixed some files from an older toolchain with some of the latest, I don't think it's a good idea.