fix devel/libev on sparc

[Tobias Ulmer <tobiasu%tmux.org@localhost>]

Stop libev from using v9 instructions on sparc v8

Index: Makefile
===================================================================
RCS file: /cvsroot/pkgsrc/devel/libev/Makefile,v
retrieving revision 1.22
diff -u -p -r1.22 Makefile
--- Makefile	22 Mar 2020 16:01:46 -0000	1.22
+++ Makefile	23 May 2020 15:49:26 -0000
@@ -17,4 +17,11 @@ CONFIGURE_ARGS+=		--includedir=${PREFIX}
 CONFIGURE_ENV.SunOS+=		ac_cv_header_sys_inotify_h=no
 CONFIGURE_ENV.SunOS+=		ac_cv_header_sys_epoll_h=no
 
+.include "../../mk/bsd.prefs.mk"
+
+.if !empty(MACHINE_PLATFORM:MNetBSD-*-sparc)
+# Prevent ev.c from using v9 memory barrier instructions
+CPPFLAGS+=	-D__sparc_v8__=1
+.endif
+
 .include "../../mk/bsd.pkg.mk"