rocksdb: changes to support 'make analyze' in Jenkins

Summary:
* Updated Makefile to exit `make analyze` with status 1 if scan-build detected any bugs.
* scan-build automatically detects which c++ compiler to use, and some times is uses wrong ones (from $CPP). Added implicit parameters to use $CC and $CXX.
* Added `scan_build_report` directory to .gitignore file.
* Added `scan_build_report` directory to clean target.

Test Plan:
Run `make analyze` and verify that exit status is 1, if there are scan-build bugs detected.
Run `make clean` and verify that files in `scan_build_report` directory are deleted.
After running `make analyze; git status` and verify that no untracked files in `scan_build_report` directory.

Reviewers: meyering, sdong, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D33831

.gitignore

@@ -48,3 +48,5 @@ java/crossbuild/.vagrant
 .vagrant/
 java/**.asc
 java/javadoc
+
+scan_build_report/

Makefile

@@ -358,9 +358,11 @@ valgrind_check: all $(PROGRAMS) $(TESTS)
 		echo $$t $$((etime - stime)) >> $(VALGRIND_DIR)/valgrind_tests_times; \
 	done
 
-analyze:
-	$(MAKE) clean
-	$(CLANG_SCAN_BUILD) --use-analyzer=$(CLANG_ANALYZER) -o $(CURDIR)/scan_build_report $(MAKE) all -j32
+analyze: clean
+	$(CLANG_SCAN_BUILD) --use-analyzer=$(CLANG_ANALYZER) \
+		--use-c++=$(CXX) --use-cc=$(CC) --status-bugs \
+		-o $(CURDIR)/scan_build_report \
+		$(MAKE) dbg
 
 unity.cc:
 	$(shell (export ROCKSDB_ROOT="$(CURDIR)"; "$(CURDIR)/build_tools/unity" "$(CURDIR)/unity.cc"))
@@ -369,11 +371,12 @@ unity: unity.o
 	$(AM_LINK)
 
 clean:
-	-rm -f $(PROGRAMS) $(TESTS) $(LIBRARY) $(SHARED) make_config.mk unity.cc
-	-rm -rf ios-x86/* ios-arm/*
-	-find . -name "*.[oda]" -exec rm {} \;
-	-find . -type f -regex ".*\.\(\(gcda\)\|\(gcno\)\)" -exec rm {} \;
-	-rm -rf bzip2* snappy* zlib*
+	rm -f $(PROGRAMS) $(TESTS) $(LIBRARY) $(SHARED) make_config.mk unity.cc
+	rm -rf ios-x86 ios-arm scan_build_report
+	find . -name "*.[oda]" -exec rm {} \;
+	find . -type f -regex ".*\.\(\(gcda\)\|\(gcno\)\)" -exec rm {} \;
+	rm -rf bzip2* snappy* zlib*
+
 tags:
 	ctags * -R
 	cscope -b `find . -name '*.cc'` `find . -name '*.h'`