findstring is not prefix-safe (i.e. android matches android-log). On
the other hand filter matches words separated by whitespace and if no
wildcard (%) is used the full word has to match.
# helper macros to only add source files for plugins included in the list above
# source files are relative to the android.mk that called the macro
-plugin_enabled = $(findstring $(1), $(strongswan_PLUGINS))
+plugin_enabled = $(filter $(1), $(strongswan_PLUGINS))
add_plugin = $(if $(call plugin_enabled,$(1)), \
$(patsubst $(LOCAL_PATH)/%,%, \
$(wildcard \