Hide SO_PASSCRED and SO_PEERCRED by default.

This cause in some software to assume we are linux, as this is rightly
only used there.

By default hide it behind _MINIX_SYSTEM, until we have removed traces
of it from getpeereid/[gs]etsocketopt and replaced it by the NetBSD
mechanism.

Change-Id: Iacd4cc1b152bcb7e90f5b1249185a222c90351d6

lib/libc/net/Makefile.inc

@@ -4,6 +4,10 @@
 # net sources
 .if defined(__MINIX)
 .PATH: ${.CURDIR}/net/minix
+
+CPPFLAGS.getpeereid.c+= -D_MINIX_SYSTEM=1
+CPPFLAGS.getsockopt.c+= -D_MINIX_SYSTEM=1
+CPPFLAGS.setsockopt.c+= -D_MINIX_SYSTEM=1
 .endif
 .PATH: ${ARCHDIR}/net ${.CURDIR}/net
 

sys/sys/socket.h

@@ -131,7 +131,8 @@ typedef	_BSD_SSIZE_T_	ssize_t;
 #define	SO_ACCEPTFILTER	0x1000		/* there is an accept filter */
 #define	SO_TIMESTAMP	0x2000		/* timestamp received dgram traffic */
 
-#if defined(__minix)
+#if defined(__minix) && defined(_MINIX_SYSTEM)
+/* Minixism which should go, so hide it from userland. */
 #define SO_PASSCRED    0x100000
 #define SO_PEERCRED    0x200000
 #endif /* defined(__minix) */

test/Makefile

@@ -26,6 +26,8 @@ COPTS.test51.c=	-mhard-float
 COPTS.test52.c=	-mhard-float
 .endif
 
+CPPFLAGS.test56.c += -D_MINIX_SYSTEM=1
+
 WARNS=
 COPTS.test9.c=	-O0
 COPTS.test37.c=	-O0