build problems

Can someone lend me a hand with solving this error? Thanks.

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make[2]: Entering directory `/tmp/shadow-4.0.10/src'
/bin/sh ../libtool --tag=CC --mode=link gcc -g -O2 -o login
login.ologin_nopam.o ../libmisc/libmisc.a ../lib/libshadow.la
gcc -g -O2 -o login login.o login_nopam.o ../libmisc/libmisc.a 
../lib/.libs/libshadow.a
../lib/.libs/libshadow.a(encrypt.o)(.text+0x16): In function `pw_encrypt':
/tmp/shadow-4.0.10/lib/encrypt.c:42: undefined reference to `crypt'
collect2: ld returned 1 exit status
make[2]: *** [login] Error 1
make[2]: Leaving directory `/tmp/shadow-4.0.10/src'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/tmp/shadow-4.0.10'
make: *** [all] Error 2