interpolate sqlite3 lib in krb5-config

Commit 7e6b558d2a261228806c0998f3be83985bb1bf3e updated krb5-config to
include sqlite. However, the value was not actually being
interpolated if a user ran ./configure --with-sqlite3=/foo.

Add @LIB_sqlite3@ to the list of values that get interpolated during the
krb5-config build.