Make internal libevhtp optional.

Useful for packaging, when the target already has a libevhtp package. To
use:
make USE_INTERNAL_LIBEVHTP=0

Change-Id: Ia23c6ad9da67eb58ebfd710aa0a3b402408df6d1
Reviewed-on: https://weave-review.googlesource.com/2461
Reviewed-by: Vitaly Buka <vitalybuka@google.com>

Makefile

diff --git a/Makefile b/Makefile
index df27b58..9810dd0 100644
--- a/Makefile
+++ b/Makefile
@@ -37,7 +37,7 @@
 	-Wwrite-strings
 
 CFLAGS_Debug := \
-	-O0   \
+	-O0 \
 	-g3
 
 CFLAGS_Release := \

examples/examples.mk

diff --git a/examples/examples.mk b/examples/examples.mk
index f1e92b6..af15d5c 100644
--- a/examples/examples.mk
+++ b/examples/examples.mk
@@ -7,7 +7,13 @@
 
 examples_provider_obj_files := $(EXAMPLES_PROVIDER_SRC_FILES:%.cc=out/$(BUILD_MODE)/%.o)
 
-$(examples_provider_obj_files) : out/$(BUILD_MODE)/%.o : %.cc third_party/include/evhtp.h
+USE_INTERNAL_LIBEVHTP ?= 1
+
+ifeq (1, $(USE_INTERNAL_LIBEVHTP))
+$(examples_provider_obj_files) : third_party/include/evhtp.h
+endif
+
+$(examples_provider_obj_files) : out/$(BUILD_MODE)/%.o : %.cc
 	mkdir -p $(dir $@)
 	$(CXX) $(DEFS_$(BUILD_MODE)) $(INCLUDES) $(CFLAGS) $(CFLAGS_$(BUILD_MODE)) $(CFLAGS_CC) -c -o $@ $<
 
@@ -15,7 +21,21 @@
 	rm -f $@
 	$(AR) crsT $@ $^
 
-out/$(BUILD_MODE)/examples/daemon/%.o : examples/daemon/%.cc third_party/include/evhtp.h
+EXAMPLES_DAEMON_SRC_FILES := \
+	examples/daemon/ledflasher/ledflasher.cc \
+	examples/daemon/light/light.cc \
+	examples/daemon/lock/lock.cc \
+	examples/daemon/oven/oven.cc \
+	examples/daemon/sample/sample.cc \
+	examples/daemon/speaker/speaker.cc
+
+examples_daemon_obj_files := $(EXAMPLES_DAEMON_SRC_FILES:%.cc=out/$(BUILD_MODE)/%.o)
+
+ifeq (1, $(USE_INTERNAL_LIBEVHTP))
+$(examples_daemon_obj_files) : third_party/include/evhtp.h
+endif
+
+$(examples_daemon_obj_files) : out/$(BUILD_MODE)/%.o : %.cc
 	mkdir -p $(dir $@)
 	$(CXX) $(DEFS_$(BUILD_MODE)) $(INCLUDES) $(CFLAGS) $(CFLAGS_$(BUILD_MODE)) $(CFLAGS_CC) -c -o $@ $<
 
@@ -32,22 +52,30 @@
 	-lssl \
 	-lcrypto
 
-out/$(BUILD_MODE)/weave_daemon_ledflasher : out/$(BUILD_MODE)/examples/daemon/ledflasher/ledflasher.o out/$(BUILD_MODE)/examples_provider.a out/$(BUILD_MODE)/libweave.so third_party/lib/libevhtp.a
+daemon_deps := out/$(BUILD_MODE)/examples_provider.a out/$(BUILD_MODE)/libweave.so
+
+ifeq (1, $(USE_INTERNAL_LIBEVHTP))
+daemon_deps += third_party/lib/libevhtp.a
+else
+daemon_common_flags += -levhtp
+endif
+
+out/$(BUILD_MODE)/weave_daemon_ledflasher : out/$(BUILD_MODE)/examples/daemon/ledflasher/ledflasher.o $(daemon_deps)
 	$(CXX) -o $@ $^ $(CFLAGS) $(daemon_common_flags)
 
-out/$(BUILD_MODE)/weave_daemon_light : out/$(BUILD_MODE)/examples/daemon/light/light.o out/$(BUILD_MODE)/examples_provider.a out/$(BUILD_MODE)/libweave.so third_party/lib/libevhtp.a
+out/$(BUILD_MODE)/weave_daemon_light : out/$(BUILD_MODE)/examples/daemon/light/light.o $(daemon_deps)
 	$(CXX) -o $@ $^ $(CFLAGS) $(daemon_common_flags)
 
-out/$(BUILD_MODE)/weave_daemon_lock : out/$(BUILD_MODE)/examples/daemon/lock/lock.o out/$(BUILD_MODE)/examples_provider.a out/$(BUILD_MODE)/libweave.so third_party/lib/libevhtp.a
+out/$(BUILD_MODE)/weave_daemon_lock : out/$(BUILD_MODE)/examples/daemon/lock/lock.o $(daemon_deps)
 	$(CXX) -o $@ $^ $(CFLAGS) $(daemon_common_flags)
 
-out/$(BUILD_MODE)/weave_daemon_oven : out/$(BUILD_MODE)/examples/daemon/oven/oven.o out/$(BUILD_MODE)/examples_provider.a out/$(BUILD_MODE)/libweave.so third_party/lib/libevhtp.a
+out/$(BUILD_MODE)/weave_daemon_oven : out/$(BUILD_MODE)/examples/daemon/oven/oven.o $(daemon_deps)
 	$(CXX) -o $@ $^ $(CFLAGS) $(daemon_common_flags)
 
-out/$(BUILD_MODE)/weave_daemon_sample : out/$(BUILD_MODE)/examples/daemon/sample/sample.o out/$(BUILD_MODE)/examples_provider.a out/$(BUILD_MODE)/libweave.so third_party/lib/libevhtp.a
+out/$(BUILD_MODE)/weave_daemon_sample : out/$(BUILD_MODE)/examples/daemon/sample/sample.o $(daemon_deps)
 	$(CXX) -o $@ $^ $(CFLAGS) $(daemon_common_flags)
 
-out/$(BUILD_MODE)/weave_daemon_speaker : out/$(BUILD_MODE)/examples/daemon/speaker/speaker.o out/$(BUILD_MODE)/examples_provider.a out/$(BUILD_MODE)/libweave.so third_party/lib/libevhtp.a
+out/$(BUILD_MODE)/weave_daemon_speaker : out/$(BUILD_MODE)/examples/daemon/speaker/speaker.o $(daemon_deps)
 	$(CXX) -o $@ $^ $(CFLAGS) $(daemon_common_flags)
 
 all-examples : out/$(BUILD_MODE)/weave_daemon_ledflasher out/$(BUILD_MODE)/weave_daemon_light out/$(BUILD_MODE)/weave_daemon_lock out/$(BUILD_MODE)/weave_daemon_oven out/$(BUILD_MODE)/weave_daemon_sample out/$(BUILD_MODE)/weave_daemon_speaker