this is actually for version 0.9.29 which is not listed in the versions box. trying to compile buildroot 2009.02, when i get to the point where some network stuff is compiling, i get conflicts between uClibc-0.9.29/include/bits/kernel_types.h and linux/include/asm/posix_types_32.h (included by linux/include/asm/posix_types.h on a 32-bit system). this is because the #define masks in kernel_types.h are: #define _ASM_X86_64_POSIX_TYPES_H #define __ARCH_I386_POSIX_TYPES_H but the mask actually used in posix_types_32.h is: #define _ASM_X86_POSIX_TYPES_32_H adding this mask to kernel_types.h allows compilation to continue. this is for kernel header files from 2.6.28.4, i think... at least thats what buildroot said it was downloading.
this bug also applies on x64. i added the line: #define _ASM_X86_POSIX_TYPES_64_H to uClibc-0.9.29/include/bits/kernel_types.h as a workaround.
this is fixed already in the latest version of uClibc. you should upgrade.