Allow boostrapping xinstall on Linux

Linux does not have st_flags so we have to avoid using it there.

Reviewed By:	emaste, imp
Differential Revision: https://reviews.freebsd.org/D22446

usr.bin/xinstall/Makefile

@@ -11,7 +11,6 @@ MAN=		install.1
 .PATH:		${SRCTOP}/contrib/mtree
 CFLAGS+=	-I${SRCTOP}/contrib/mtree
 CFLAGS+=	-I${SRCTOP}/lib/libnetbsd
-CFLAGS+=	-DHAVE_STRUCT_STAT_ST_FLAGS=1
 
 LIBADD=	md
 

usr.bin/xinstall/xinstall.c

@@ -75,6 +75,17 @@ __FBSDID("$FreeBSD$");
 
 #include "mtree.h"
 
+/*
+ * We need to build xinstall during the bootstrap stage when building on a
+ * non-FreeBSD system. Linux does not have the st_flags and st_birthtime
+ * members in struct stat so we need to omit support for changing those fields.
+ */
+#ifdef UF_SETTABLE
+#define HAVE_STRUCT_STAT_ST_FLAGS 1
+#else
+#define HAVE_STRUCT_STAT_ST_FLAGS 0
+#endif
+
 #define MAX_CMP_SIZE	(16 * 1024 * 1024)
 
 #define	LN_ABSOLUTE	0x01