Description: Keep hardening build flags.
Author: Martin Steigerwald <martin.steigerwald@proact.de>

--- a/Makefile
+++ b/Makefile
@@ -20,9 +20,9 @@
 endif
 
 DEBUGFLAGS = -DFIO_INC_DEBUG
-CPPFLAGS= -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -DFIO_INTERNAL $(DEBUGFLAGS)
+CPPFLAGS+= -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -DFIO_INTERNAL $(DEBUGFLAGS)
 OPTFLAGS= -g -ffast-math
-CFLAGS	= -std=gnu99 -Wwrite-strings -Wall -Wdeclaration-after-statement $(OPTFLAGS) $(EXTFLAGS) $(BUILD_CFLAGS) -I. -I$(SRCDIR)
+CFLAGS	+= -std=gnu99 -Wwrite-strings -Wall -Wdeclaration-after-statement $(OPTFLAGS) $(EXTFLAGS) $(BUILD_CFLAGS) -I. -I$(SRCDIR)
 LIBS	+= -lm $(EXTLIBS)
 PROGS	= fio
 SCRIPTS = $(addprefix $(SRCDIR)/,tools/fio_generate_plots tools/plot/fio2gnuplot tools/genfio tools/fiologparser.py tools/hist/fiologparser_hist.py tools/fio_jsonplus_clat2csv)
