Compile error - library 'crypto' is required for OpenSSL

Hi. I am trying to compile squid with --enable-ssl-crtd, but facing the mentioned error. The Makefile used can be seen below:

#
# Copyright (C) 2006-2015 OpenWrt.org
#
# This is free software, licensed under the GNU General Public License v2.
# See /LICENSE for more information.
#

include $(TOPDIR)/rules.mk

PKG_NAME:=squid
PKG_VERSION:=3.5.27
PKG_RELEASE:=1

PKG_LICENSE:=GPL-2.0
PKG_MAINTAINER:=Marko Ratkaj <marko.ratkaj@sartura.hr>

PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.xz
PKG_SOURCE_URL:=http://www3.us.squid-cache.org/Versions/v3/3.5/ \
	http://www2.pl.squid-cache.org/Versions/v3/3.5/ \
	http://www.squid-cache.org/Versions/v3/3.5/
PKG_HASH:=5ddb4367f2dc635921f9ca7a59d8b87edb0412fa203d1543393ac3c7f9fef0ec

PKG_BUILD_PARALLEL:=1
PKG_INSTALL:=1

include $(INCLUDE_DIR)/package.mk

define Package/squid/Default
  SECTION:=net
  CATEGORY:=Network
  SUBMENU:=Web Servers/Proxies
  URL:=http://www.squid-cache.org/
  MENU:=1
endef

define Package/squid
  $(call Package/squid/Default)
  DEPENDS:=+libopenssl +libpthread +librt +libltdl +libstdcpp
  TITLE:=full-featured Web proxy cache
endef

define Package/squid/description
  Squid is a caching proxy for the Web supporting HTTP, HTTPS, FTP, and more.
  It reduces bandwidth and improves response times by caching and reusing
  frequently-requested web pages.
endef

define Package/squid-mod-cachemgr
  $(call Package/squid/Default)
  DEPENDS:=squid
  TITLE:=Web based proxy manager and reporting tool
endef

CONFIGURE_ARGS += \
	--config-cache \
	--datadir=/usr/share/squid \
	--libexecdir=/usr/lib/squid \
	--sysconfdir=/etc/squid \
	--enable-shared \
	--disable-static \
	--enable-icmp \
	--enable-delay-pools \
	--enable-icap-client \
	--enable-kill-parent-hack \
	--disable-snmp \
	--enable-ssl \
	--enable-ssl-crtd \
	--enable-cache-digests \
	--enable-linux-netfilter \
	--disable-unlinkd \
	--enable-x-accelerator-vary \
	--disable-translation \
	--disable-auto-locale \
	--with-dl \
	--with-pthreads \
	--without-expat \
	--without-libxml2 \
	--without-gnutls \
	--without-nettle \
	--with-openssl=$(STAGING_DIR)/usr \
	--enable-epoll \
	--with-maxfd=4096 \
	--enable-external-acl-helpers \
	--disable-auth-negotiate \
	--disable-auth-ntlm \
	--disable-auth-digest \
	--enable-auth-basic \
	--disable-arch-native \
	--with-krb5-config=no \
	--without-mit-krb5 \
	--without-libcap \
	--without-netfilter-conntrack

CONFIGURE_VARS += \
	ac_cv_header_linux_netfilter_ipv4_h=yes \
	ac_cv_epoll_works=yes \
	squid_cv_gnu_atomics=no

define Build/Compile
	+$(MAKE) $(PKG_JOBS) -C $(PKG_BUILD_DIR)/lib all
	+$(MAKE) $(PKG_JOBS) -C $(PKG_BUILD_DIR) \
		DESTDIR="$(PKG_INSTALL_DIR)" \
		install
endef

define Package/squid/install
	$(INSTALL_DIR) $(1)/usr/sbin
	$(INSTALL_BIN) $(PKG_INSTALL_DIR)/usr/sbin/squid $(1)/usr/sbin/

	$(INSTALL_DIR) $(1)/usr/lib/squid
	$(INSTALL_BIN) $(PKG_INSTALL_DIR)/usr/lib/squid/ssl_crtd $(1)/usr/lib/squid
	$(INSTALL_BIN) $(PKG_INSTALL_DIR)/usr/lib/squid/basic_db_auth $(1)/usr/lib/squid
	$(INSTALL_BIN) $(PKG_INSTALL_DIR)/usr/lib/squid/basic_fake_auth $(1)/usr/lib/squid
	$(INSTALL_BIN) $(PKG_INSTALL_DIR)/usr/lib/squid/basic_getpwnam_auth $(1)/usr/lib/squid
	$(INSTALL_BIN) $(PKG_INSTALL_DIR)/usr/lib/squid/basic_msnt_multi_domain_auth $(1)/usr/lib/squid
	$(INSTALL_BIN) $(PKG_INSTALL_DIR)/usr/lib/squid/basic_ncsa_auth $(1)/usr/lib/squid
	$(INSTALL_BIN) $(PKG_INSTALL_DIR)/usr/lib/squid/basic_pop3_auth $(1)/usr/lib/squid
	$(INSTALL_BIN) $(PKG_INSTALL_DIR)/usr/lib/squid/basic_radius_auth $(1)/usr/lib/squid
	$(INSTALL_BIN) $(PKG_INSTALL_DIR)/usr/lib/squid/basic_smb_auth $(1)/usr/lib/squid
	$(INSTALL_BIN) $(PKG_INSTALL_DIR)/usr/lib/squid/basic_smb_auth.sh $(1)/usr/lib/squid
	$(INSTALL_BIN) $(PKG_INSTALL_DIR)/usr/lib/squid/basic_smb_lm_auth $(1)/usr/lib/squid

	$(INSTALL_DIR) $(1)/etc/config
	$(INSTALL_CONF) ./files/squid.config $(1)/etc/config/squid

	$(INSTALL_DIR) $(1)/etc/squid
	$(INSTALL_CONF) $(PKG_INSTALL_DIR)/etc/squid/mime.conf $(1)/etc/squid/
	$(INSTALL_CONF) ./files/squid.conf $(1)/etc/squid/

	$(INSTALL_DIR) $(1)/etc/init.d/
	$(INSTALL_BIN) ./files/squid.init $(1)/etc/init.d/squid

	$(INSTALL_DIR) $(1)/usr/share/squid/icons/
	$(CP) $(PKG_INSTALL_DIR)/usr/share/squid/icons/* $(1)/usr/share/squid/icons/

	$(INSTALL_DIR) $(1)/usr/share/squid/errors/templates/
	$(CP) $(PKG_INSTALL_DIR)/usr/share/squid/errors/templates/* $(1)/usr/share/squid/errors/templates/
endef

define Package/squid-mod-cachemgr/install
	$(INSTALL_DIR) $(1)/www/cgi-bin/
	$(CP) $(PKG_INSTALL_DIR)/usr/lib/squid/cachemgr.cgi $(1)/www/cgi-bin/
endef

$(eval $(call BuildPackage,squid))
$(eval $(call BuildPackage,squid-mod-cachemgr))

Error:

checking for CRYPTO_new_ex_data in -lcrypto... no
configure: error: library 'crypto' is required for OpenSSL
Makefile:145: recipe for target '/home/openwrt-sdk/build_dir/target-arm_cortex-a9+vfpv3-d16_musl_eabi/squid-3.5.27/.configured_68b329da9893e34099c7d8ad5cb9c940' failed
make[2]: *** [/home/openwrt-sdk/build_dir/target-arm_cortex-a9+vfpv3-d16_musl_eabi/squid-3.5.27/.configured_68b329da9893e34099c7d8ad5cb9c940] Error 1
make[2]: Leaving directory '/home/openwrt-sdk/package/my_packages/squid'
time: package/my_packages/squid/compile#5.68#12.11#151.01
package/Makefile:111: recipe for target 'package/my_packages/squid/compile' failed
make[1]: *** [package/my_packages/squid/compile] Error 2
make[1]: Leaving directory '/home/openwrt-sdk'
/home/openwrt-sdk/include/toplevel.mk:218: recipe for target 'package/my_packages/squid/compile' failed
make: *** [package/my_packages/squid/compile] Error 2

Grateful for any assistance given to help rectify the issue.