use separate variable name for benchmark 'size' in makefile to avoid …

…altering default test size (#3806)

Signed-off-by: Jeremiah Corrado <jeremiah.corrado@hpe.com>

Makefile

@@ -568,10 +568,10 @@ CLEAN_TARGETS += test-clean
 test-clean:
 	$(RM) $(TEST_TARGETS) $(addsuffix _real,$(TEST_TARGETS))
 
-size = 10**8
+size_bm = 10**8
 .PHONY: benchmark
 benchmark:
-	python3 -m pytest -c benchmark.ini --benchmark-autosave --benchmark-storage=file://benchmark_v2/.benchmarks --size=$(size)
+	python3 -m pytest -c benchmark.ini --benchmark-autosave --benchmark-storage=file://benchmark_v2/.benchmarks --size=$(size_bm)
 
 version:
 	@echo $(VERSION);