Add tempfile() - a secure tmpfile() replacement using O_TMPFILE.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Makefile

@@ -38,6 +38,7 @@ STRIPINST  := $(INSTALL) -s --strip-program=$(CROSS)strip -m 0755
 
 CFLAGS     += -fPIC
 CFLAGS     += -Os
+CPPFLAGS   += -D_GNU_SOURCE
 CPPFLAGS   += -W -Wall -Werror
 ARFLAGS     = crus
 MAKEFLAGS   = --no-print-directory --silent
@@ -45,7 +46,7 @@ MAKEFLAGS   = --no-print-directory --silent
 DISTFILES   = README LICENSE
 HEADERS     = lite.h
 OBJS       := chomp.o copyfile.o dir.o fexist.o fisdir.o fmode.o rsync.o
-OBJS       += strlcpy.o strlcat.o strtonum.o
+OBJS       += strlcpy.o strlcat.o strtonum.o tempfile.o
 DEPS       := $(OBJS:.o=.d)
 JUNK        = *~ *.bak *.map .*.d *.d DEADJOE semantic.cache *.gdb *.elf core core.*