uml: implement O_APPEND

The .a flags in openflags never had an implementation.

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/um/os-Linux/file.c b/arch/um/os-Linux/file.c
index d7404c6..b5afcfd 100644
--- a/arch/um/os-Linux/file.c
+++ b/arch/um/os-Linux/file.c
@@ -191,6 +191,8 @@
 		f |= O_TRUNC;
 	if (flags.e)
 		f |= O_EXCL;
+	if (flags.a)
+		f |= O_APPEND;
 
 	fd = open64(file, f, mode);
 	if (fd < 0)