syscall: add WASI {D,R}SYNC, NONBLOCK FD flags

Signed-off-by: Roman Volosatovs <roman@profian.com>

src/syscall/syscall_libc_wasi.go

@@ -55,6 +55,9 @@ const (
 	__WASI_OFLAGS_TRUNC = 8
 
 	__WASI_FDFLAGS_APPEND   = 1
+	__WASI_FDFLAGS_DSYNC    = 2
+	__WASI_FDFLAGS_NONBLOCK = 4
+	__WASI_FDFLAGS_RSYNC    = 8
 	__WASI_FDFLAGS_SYNC     = 16
 
 	O_RDONLY = 0x04000000
@@ -66,6 +69,9 @@ const (
 	O_EXCL  = __WASI_OFLAGS_EXCL << 12
 
 	O_APPEND   = __WASI_FDFLAGS_APPEND
+	O_DSYNC    = __WASI_FDFLAGS_DSYNC
+	O_NONBLOCK = __WASI_FDFLAGS_NONBLOCK
+	O_RSYNC    = __WASI_FDFLAGS_RSYNC
 	O_SYNC     = __WASI_FDFLAGS_SYNC
 
 	O_CLOEXEC = 0