Extracted some parts from Android.mk.in which can be used for NDK builds.

Android.mk

@@ -0,0 +1,118 @@
+LOCAL_PATH := $(call my-dir)
+include $(CLEAR_VARS)
+
+# the executables that should be installed on the final system have to be added
+# to PRODUCT_PACKAGES in
+#   build/target/product/core.mk
+# possible executables are
+#   starter - allows to control and configure the daemon from the command line
+#   charon - the IKE daemon
+#   scepclient - SCEP client
+
+# if you enable starter or scepclient (see above) uncomment the proper
+# lines here
+# strongswan_BUILD_STARTER := true
+# strongswan_BUILD_SCEPCLIENT := true
+
+# this is the list of plugins that are built into libstrongswan and charon
+# also these plugins are loaded by default (if not changed in strongswan.conf)
+strongswan_CHARON_PLUGINS := android-log openssl fips-prf random nonce pubkey \
+	pkcs1 pem xcbc hmac kernel-netlink socket-default android \
+	stroke eap-identity eap-mschapv2 eap-md5
+
+ifneq ($(strongswan_BUILD_SCEPCLIENT),)
+# plugins loaded by scepclient
+strongswan_SCEPCLIENT_PLUGINS := openssl curl fips-prf random pkcs1 pem
+endif
+
+strongswan_STARTER_PLUGINS := kernel-netlink
+
+# list of all plugins - used to enable them with the function below
+strongswan_PLUGINS := $(sort $(strongswan_CHARON_PLUGINS) \
+			     $(strongswan_STARTER_PLUGINS) \
+			     $(strongswan_SCEPCLIENT_PLUGINS))
+
+include $(LOCAL_PATH)/Android.common.mk
+
+# includes
+strongswan_PATH := $(LOCAL_PATH)
+libvstr_PATH := external/strongswan-support/vstr/include
+libcurl_PATH := external/strongswan-support/libcurl/include
+libgmp_PATH := external/strongswan-support/gmp
+openssl_PATH := external/openssl/include
+
+# some definitions
+strongswan_DIR := "/system/bin"
+strongswan_SBINDIR := "/system/bin"
+strongswan_PIDDIR := "/data/misc/vpn"
+strongswan_PLUGINDIR := "$(strongswan_IPSEC_DIR)/ipsec"
+strongswan_CONFDIR := "/system/etc"
+strongswan_STRONGSWAN_CONF := "$(strongswan_CONFDIR)/strongswan.conf"
+
+# CFLAGS (partially from a configure run using droid-gcc)
+strongswan_CFLAGS := \
+	-Wno-format \
+	-Wno-pointer-sign \
+	-Wno-pointer-arith \
+	-Wno-sign-compare \
+	-Wno-strict-aliasing \
+	-DHAVE___BOOL \
+	-DHAVE_STDBOOL_H \
+	-DHAVE_ALLOCA_H \
+	-DHAVE_ALLOCA \
+	-DHAVE_CLOCK_GETTIME \
+	-DHAVE_PTHREAD_COND_TIMEDWAIT_MONOTONIC \
+	-DHAVE_PRCTL \
+	-DHAVE_LINUX_UDP_H \
+	-DHAVE_STRUCT_SADB_X_POLICY_SADB_X_POLICY_PRIORITY \
+	-DHAVE_IPSEC_MODE_BEET \
+	-DHAVE_IPSEC_DIR_FWD \
+	-DOPENSSL_NO_EC \
+	-DOPENSSL_NO_ECDSA \
+	-DOPENSSL_NO_ECDH \
+	-DOPENSSL_NO_ENGINE \
+	-DCONFIG_H_INCLUDED \
+	-DCAPABILITIES \
+	-DCAPABILITIES_NATIVE \
+	-DMONOLITHIC \
+	-DUSE_IKEV1 \
+	-DUSE_IKEV2 \
+	-DUSE_VSTR \
+	-DDEBUG \
+	-DROUTING_TABLE=0 \
+	-DROUTING_TABLE_PRIO=220 \
+	-DVERSION=\"$(strongswan_VERSION)\" \
+	-DPLUGINDIR=\"$(strongswan_PLUGINDIR)\" \
+	-DIPSEC_DIR=\"$(strongswan_DIR)\" \
+	-DIPSEC_PIDDIR=\"$(strongswan_PIDDIR)\" \
+	-DIPSEC_CONFDIR=\"$(strongswan_CONFDIR)\" \
+	-DSTRONGSWAN_CONF=\"$(strongswan_STRONGSWAN_CONF)\" \
+	-DDEV_RANDOM=\"/dev/random\" \
+	-DDEV_URANDOM=\"/dev/urandom\"
+
+# only for Android 2.0+
+strongswan_CFLAGS += \
+	-DHAVE_IN6ADDR_ANY
+
+strongswan_BUILD := \
+	charon \
+	libcharon \
+	libhydra \
+	libstrongswan \
+	libtncif \
+	libtnccs
+
+ifneq ($(strongswan_BUILD_STARTER),)
+strongswan_BUILD += \
+	starter \
+	stroke \
+	ipsec
+endif
+
+ifneq ($(strongswan_BUILD_SCEPCLIENT),)
+strongswan_BUILD += \
+	scepclient
+endif
+
+include $(addprefix $(LOCAL_PATH)/src/,$(addsuffix /Android.mk, \
+		$(sort $(strongswan_BUILD))))