DAOS-1310 Build raft using the Makefile target

Currently we build raft by [re]defining it's build recipe in an
SConsscript file. This will leave us continually chasing changes
upstream makes in how it's built.

Instead, we should use the make target supplied by the upstream
Makefile.

While we are at it, we might as well use the Makefile to build the
test_main test tool so that it doesn't have to be done at test run-time.

To continue to support our Variant building with scons, add support to
the raft Makefile for building into a separate named directory.

Add a call to "make clean" when scons -c is run to clean up the build
product.

Add the ability to disable gcov support in the raft Makefile and
disable it during our build from scons.

Makefile

@@ -2,9 +2,10 @@ CONTRIB_DIR = .
 TEST_DIR = ./tests
 LLQUEUE_DIR = $(CONTRIB_DIR)/CLinkedListQueue
 VPATH = src
+BUILDDIR ?= .
 
-GCOV_OUTPUT = *.gcda *.gcno *.gcov 
-GCOV_CCFLAGS = -fprofile-arcs -ftest-coverage
+GCOV_OUTPUT = $(BUILDDIR)/*.gcda $(BUILDDIR)/*.gcno $(BUILDDIR)/*.gcov
+GCOV_CCFLAGS ?= -fprofile-arcs -ftest-coverage
 SHELL  = /bin/bash
 CFLAGS += -Iinclude -Werror -Werror=return-type -Werror=uninitialized -Wcast-align \
 	  -Wno-pointer-sign -fno-omit-frame-pointer -fno-common -fsigned-char \
@@ -25,10 +26,16 @@ SHAREDFLAGS = -shared
 SHAREDEXT = so
 endif
 
-OBJECTS = raft_server.o raft_server_properties.o raft_node.o raft_log.o
+OBJECTS = $(BUILDDIR)/raft_server.o $(BUILDDIR)/raft_server_properties.o $(BUILDDIR)/raft_node.o $(BUILDDIR)/raft_log.o
 
 all: static shared
 
+$(BUILDDIR):
+	mkdir -p $@
+
+$(BUILDDIR)/%.o: %.c | $(BUILDDIR)
+	$(CC) $(CFLAGS) -c -o $@ $<
+
 clinkedlistqueue:
 	mkdir -p $(LLQUEUE_DIR)/.git
 	git --git-dir=$(LLQUEUE_DIR)/.git init 
@@ -45,19 +52,21 @@ $(TEST_DIR)/main_test.c:
 
 .PHONY: shared
 shared: $(OBJECTS)
-	$(CC) $(OBJECTS) $(LDFLAGS) $(CFLAGS) -fPIC $(SHAREDFLAGS) -o libraft.$(SHAREDEXT)
+	$(CC) $(OBJECTS) $(LDFLAGS) $(CFLAGS) -fPIC $(SHAREDFLAGS) -o $(BUILDDIR)/libraft.$(SHAREDEXT)
 
 .PHONY: static
 static: $(OBJECTS)
-	ar -r libraft.a $(OBJECTS)
+	ar -r $(BUILDDIR)/libraft.a $(OBJECTS)
 
 tests_main: src/raft_server.c src/raft_server_properties.c src/raft_log.c src/raft_node.c $(TEST_DIR)/main_test.c $(TEST_DIR)/test_server.c $(TEST_DIR)/test_node.c $(TEST_DIR)/test_log.c $(TEST_DIR)/test_snapshotting.c $(TEST_DIR)/test_scenario.c $(TEST_DIR)/mock_send_functions.c $(TEST_DIR)/CuTest.c $(LLQUEUE_DIR)/linked_list_queue.c
-	$(CC) $(CFLAGS) -o $@ $^
+	$(CC) $(CFLAGS) -o $(BUILDDIR)/$@ $^
 
 .PHONY: tests
 tests: tests_main
 	./tests_main
-	gcov raft_server.c
+	if [ -n "$(GCOV_CCFLAGS)" ]; then \
+	    gcov raft_server.c;           \
+	fi
 
 .PHONY: fuzzer_tests
 fuzzer_tests:
@@ -76,7 +85,7 @@ do_infer:
 	infer -- make static
 
 clean:
-	@rm -f $(TEST_DIR)/main_test.c *.o $(GCOV_OUTPUT); \
-	if [ -f "libraft.$(SHAREDEXT)" ]; then rm libraft.$(SHAREDEXT); fi;\
-	if [ -f libraft.a ]; then rm libraft.a; fi;\
-	if [ -f tests_main ]; then rm tests_main; fi;
+	@rm -f $(TEST_DIR)/main_test.c $(BUILDDIR)/*.o $(GCOV_OUTPUT); \
+	if [ -f "$(BUILDDIR)/libraft.$(SHAREDEXT)" ]; then rm $(BUILDDIR)/libraft.$(SHAREDEXT); fi;\
+	if [ -f $(BUILDDIR)/libraft.a ]; then rm $(BUILDDIR)/libraft.a; fi;\
+	if [ -f $(BUILDDIR)/tests_main ]; then rm $(BUILDDIR)/tests_main; fi;

src/SConscript

@@ -1,6 +1,19 @@
 Import('env')
 env = env.Clone()
 env.AppendUnique(CPPPATH = ['../include'])
-env.Library('raft',
-	    ['raft_server.c', 'raft_server_properties.c', 'raft_node.c',
-	     'raft_log.c'])
+topdir = env.Dir("#").abspath
+builddir = env.Dir('.').abspath
+libraft = env.Command('libraft.a', '', 'make -C src/rdb/raft/ BUILDDIR=%s GCOV_CCFLAGS= static' % builddir)
+test_main = env.Command('tests_main', libraft, 'make -C src/rdb/raft/ BUILDDIR=%s GCOV_CCFLAGS= tests_main' % builddir)
+# even though these are AlwaysBuild() they are still inexpensive as the
+# make to build them will bail out if they don't actually need rebuilding
+AlwaysBuild(libraft)
+AlwaysBuild(test_main)
+
+def CleanAction(env, action):
+    if env.GetOption('clean'):
+        env.Execute(action)
+
+env.AddMethod(CleanAction, 'CleanAction')
+
+env.CleanAction(Action(['make -C %s/src/rdb/raft/ BUILDDIR=%s clean' % (topdir, builddir)]))