By default, Mesa appears to be quite insistent on building against X libraries. Because etnaviv is going to be an embedded GL driver, I don't want to pull the whole X11 shebang in. From the error messages it is not entirely clear how to proceed without X libs and build it, for example, for framebuffer only.

I found out that this can be done with the following configuration line:

./configure --enable-gles2 --enable-gles1 --disable-glx --enable-egl --enable-gallium-egl \
     --disable-dri --with-gallium-drivers=swrast --with-egl-platforms=fbdev

(this builds only the software rasterizer, additional gallium drivers can be specified after --with-gallium-drivers. But I'm really only interested in the GLSL->TGSI compiler for now, to have an experimental TGSI token stream input for etna_pipe)