Minor Makefile update to exclude microbench as dependency (#8523)

Summary:
Otherwise the build may report warning about missing
`benchmark.h` for some targets, the error won't break the build.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8523

Test Plan:
`make blackbox_ubsan_crash_test` on a machine without
benchmark lib installed.

Reviewed By: pdillinger

Differential Revision: D29682478

Pulled By: jay-zhuang

fbshipit-source-id: e1261fbcda46bc6bd3cd39b7b03b7f78927d0430

Makefile

@@ -506,7 +506,7 @@ STRESS_OBJECTS =  $(patsubst %.cc, $(OBJ_DIR)/%.o, $(STRESS_LIB_SOURCES))
 # Exclude build_version.cc -- a generated source file -- from all sources.  Not needed for dependencies
 ALL_SOURCES  = $(filter-out util/build_version.cc, $(LIB_SOURCES)) $(TEST_LIB_SOURCES) $(MOCK_LIB_SOURCES) $(GTEST_DIR)/gtest/gtest-all.cc
 ALL_SOURCES += $(TOOL_LIB_SOURCES) $(BENCH_LIB_SOURCES) $(CACHE_BENCH_LIB_SOURCES) $(ANALYZER_LIB_SOURCES) $(STRESS_LIB_SOURCES)
-ALL_SOURCES += $(TEST_MAIN_SOURCES) $(TOOL_MAIN_SOURCES) $(BENCH_MAIN_SOURCES) $(MICROBENCH_SOURCES)
+ALL_SOURCES += $(TEST_MAIN_SOURCES) $(TOOL_MAIN_SOURCES) $(BENCH_MAIN_SOURCES)
 
 TESTS = $(patsubst %.cc, %, $(notdir $(TEST_MAIN_SOURCES)))
 TESTS += $(patsubst %.c, %, $(notdir $(TEST_MAIN_SOURCES_C)))