Busybox: prevent compile hang

I upgrading the busybox in my openwrt sdk..
The BZIP2_SMALL option was not being exposed via Config.in which caused the build to fail as 'yes' is piped to the config during
build. As it's expecting a number, it gets stuck in a loop.

Below is the log:

Make tar, rpm, modprobe etc understand .gz data (FEATURE_SEAMLESS_GZ) [Y/n] y
Make tar, rpm, modprobe etc understand .Z data (FEATURE_SEAMLESS_Z) [N/y] n
ar (9.5 kb) (AR) [N/y/?] n
uncompress (7.1 kb) (UNCOMPRESS) [Y/n/?] y
gunzip (11 kb) (GUNZIP) [Y/n/?] y
zcat (24 kb) (ZCAT) [Y/n/?] (NEW)   Enable long options (FEATURE_GUNZIP_LONG_OPTIONS) [Y/n] (NEW) bunzip2 (8.7 kb) (BUNZIP2) [Y/n/?] y
bzcat (8.7 kb) (BZCAT) [Y/n/?] (NEW) unlzma (7.5 kb) (UNLZMA) [N/y/?] n
lzcat (7.5 kb) (LZCAT) [Y/n/?] (NEW) lzma -d (LZMA) [Y/n/?] (NEW) unxz (13 kb) (UNXZ) [Y/n/?] y
xzcat (13 kb) (XZCAT) [Y/n/?] (NEW) xz -d (XZ) [Y/n/?] y
bzip2 (16 kb) (BZIP2) [Y/n/?] y
  Trade bytes for speed (0:fast, 9:small) (BZIP2_SMALL) [8] (NEW)   Trade bytes for speed (0:fast, 9:small) (BZIP2_SMALL) [8] (NEW)   
Trade bytes for speed (0:fast, 9:small) (BZIP2_SMALL) [8] (NEW)   Trade bytes for speed (0:fast, 9:small) (BZIP2_SMALL) [8] (NEW)   T
rade bytes for speed (0:fast, 9:small) (BZIP2_SMALL) [8] (NEW)   Trade bytes for speed (0:fast, 9:small) (BZIP2_SMALL) [8] (NEW)   
Trade bytes for speed (0:fast, 9:small) (BZIP2_SMALL) [8] (NEW)   Trade bytes for speed (0:fast, 9:small) (BZIP2_SMALL) [8] (NEW) 
  Trade bytes for speed (0:fast, 9:small) (BZIP2_SMALL) [8] (NEW)   Trade bytes for speed (0:fast, 9:small) (BZIP2_SMALL) [8] (NEW) 
  Trade bytes for speed (0:fast, 9:small) (BZIP2_SMALL) [8] (NEW)   Trade bytes for speed (0:fast, 9:small