-Werror=format-security seems to be ignored without -Wformat
Thanks @ Christoph Brill
bindir ?= ${prefix}/bin
mandir ?= ${prefix}/share/man
CFLAGS ?= -O2 -g -Wall
-CFLAGS += -std=gnu99 -D_FILE_OFFSET_BITS=64 -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2
+CFLAGS += -std=gnu99 -D_FILE_OFFSET_BITS=64 -Wformat -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2
bashcompletiondir ?= ${datadir}/bash-completion/completions
man1pages = lsinitrd.1