Description of problem:
i wanted to try to build my own mesa rpms with --enable-texture-float, so that i get the advertised OpenGL 3 support, so that SecondLife (32bit application) looks more shiny... :-)
but: i cant use rpmbuild to do that...

Version-Release number of selected component (if applicable):
mesa-8.0.2-5.fc17.src.rpm
Linux vaako.riddick.homeunix.org 3.3.4-3.fc17.x86_64 #1 SMP Wed May 2 16:16:08 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux

How reproducible:
always

Steps to Reproduce:
1. install srpm
2. rpmbuild -bb --target=i686 SPECS/mesa.spec
3. linux32 rpmbuild -bb --target=i686 SPECS/mesa.spec
  
Actual results:
1. rpmbuild -bb --target=i686 SPECS/mesa.spec
g++ -Wl,-z,relro  -L/usr/lib64/llvm  -lpthread -lffi -ldl -lm  lp_test_sincos.o lp_test_main.o -o lp_test_sincos -Wl,--start-group  -L../../auxiliary/ -lgallium libllvmpipe.a -lLLVM-3.0 -lstdc++  -lXext -lXdamage -lXfixes -lX11-xcb -lX11 -lxcb-glx -lxcb -lXxf86vm   -ldrm   -lm -lpthread -ldl -Wl,--end-group
/usr/bin/ld: skipping incompatible ../../auxiliary//libgallium.a when searching for -lgallium
/usr/bin/ld: cannot find -lgallium
2. linux32 rpmbuild -bb --target=i686 SPECS/mesa.spec
/bin/sh ../../../../../bin/mklib -o nouveau_vieux_dri.so.tmp -noprefix -linker 'g++' -ldflags '-Wl,-z,relro ' \
	../common/utils.o ../common/dri_util.o ../common/xmlconfig.o nouveau_screen.o nouveau_context.o nouveau_fbo.o nouveau_driver.o nouveau_state.o nouveau_bufferobj.o nouveau_span.o nouveau_bo_state.o nouveau_texture.o nouveau_surface.o nouveau_scratch.o nouveau_array.o nv04_context.o nv04_render.o nv04_state_fb.o nv04_state_raster.o nv04_state_tex.o nv04_state_frag.o nv04_surface.o nv10_context.o nv10_render.o nv10_state_fb.o nv10_state_polygon.o nv10_state_raster.o nv10_state_tex.o nv10_state_frag.o nv10_state_tnl.o nv20_context.o nv20_render.o nv20_state_fb.o nv20_state_polygon.o nv20_state_raster.o nv20_state_tex.o nv20_state_frag.o nv20_state_tnl.o      ../../../../../src/mesa/libmesa.a -lselinux -ldrm   -lexpat -lm -lpthread -ldl -ldrm_nouveau  
mklib: Making Linux shared library:  nouveau_vieux_dri.so.tmp
/usr/bin/ld: i386 architecture of input file `../common/utils.o' is incompatible with i386:x86-64 output

Expected results:
i expected that i get the 32bit libraries for the 32bit SecondLife client...

Additional info:
maybe i didnt use rpmbuild properly?
how do u make the 32bit libs?