This happens at least for rb-2.4:
[...]
Making all in libxsupgui
gmake[8]: Entering directory `/home/n0-1/svn/freewrt-snapshot-2.4/build_mipsel/w-xsupplicant-1.2.8-1/xsupplicant-1.2.8/lib/libxsupgui'
ccache /home/n0-1/svn/freewrt-snapshot-2.4/staging_dir_mipsel/bin/mipsel-linux-uclibc-gcc -DPACKAGE_NAME=\"\" -DPACKAGE_TARNAME=\"\" -DPACKAGE_VERSION=\"\" -DPACKAGE_STRING=\"\" -DPACKAGE_BUGREPORT=\"\" -DPACKAGE=\"xsupplicant\" -DVERSION=\"1.2.8\" -DSTDC_HEADERS=1 -DLILENDIAN=1 -DHAVE_SYS_TYPES_H=1 -DHAVE_SYS_STAT_H=1 -DHAVE_STDLIB_H=1 -DHAVE_STRING_H=1 -DHAVE_MEMORY_H=1 -DHAVE_STRINGS_H=1 -DHAVE_INTTYPES_H=1 -DHAVE_STDINT_H=1 -DHAVE_UNISTD_H=1 -DNO_PWD_RESET=1 -DOPENSSL_NO_KRB5=1 -DLINUX=1 -DHAVE_SYS_SOCKET_H=1 -DHAVE_IWLIB_H=1 -DNEW_IWLIB=1 -DHAVE_LIBCRYPTO=1 -DHAVE_LIBSSL=1 -DLINUX_FRAMER=1 -I. -I. ../../src -I/home/n0-1/svn/freewrt-snapshot-2.4/staging_dir_mipsel/usr/include -I/home/n0-1/svn/freewrt-snapshot-2.4/staging_dir_mipsel/include -I/home/n0-1/svn/freewrt-snapshot-2.4/build_mipsel/w-xsupplicant-1.2.8-1/xsupplicant-1.2.8/lib/libxsupconfig/ -I/home/n0-1/svn/freewrt-snapshot-2.4/staging_dir_mipsel/usr/include/madwifi -I/home/n0-1/svn/freewrt-snapshot-2.4/staging_dir_mipsel/usr/include -Os -fno-ident -Wall -c `test -f 'xsupgui.c' || echo './'`xsupgui.c
mipsel-linux-uclibc-gcc: ../../src: linker input file unused because linking not done
mipsel-linux-uclibc-gcc: ../../src: linker input file unused because linking not done
cc1: ../../src: No such file or directory
gmake[8]: *** [xsupgui.o] Error 1
[...]
Maybe other target devices are also affected, I didn't test it.
