Scons: *** [libserf-1.dll] Error 1120 while creating Apache Serf

I tried to build Apache Serf with SCons build system https://github.com/fcharlie/serf . I have used the correct drugstores, drugstores and Openssl to create the serf. When running the following command "scons APR = C: \ Serf \ AprApu APU = C: \ Serf \ AprApu OPENSSL = C: \ Serf \ OpenSSL PREFIX = C: \ Serf \ serf-1.3.9", I got the following errors.

libserf-1.lib: fatal error LNK1120: 143 unresolved external

scons: *** [libserf-1.dll] Error 1120
scons: building terminated due to error

How do I resolve this?

Please find a screenshot of the error information: