qemu: remove 9p O_NOATIME patch

This is redundant with QEMU commit a5804fcf7b ("9pfs: local: ignore
O_NOATIME if we don't have permissions"), included in QEMU since
5.1.0, which will retry opens without O_NOATIME if they fail with it.

pkgs/applications/virtualization/qemu/9p-ignore-noatime.patch

@@ -1,49 +0,0 @@
-From 9e4932ae99946b1a08ab5b5345fd2bc3486e54a5 Mon Sep 17 00:00:00 2001
-From: aszlig <aszlig@nix.build>
-Date: Mon, 18 Mar 2019 13:21:01 +0100
-Subject: [PATCH] 9pfs: Ignore O_NOATIME open flag
-
-Since Linux 4.19, overlayfs uses the O_NOATIME flag on its lowerdir,
-which in turn causes errors when the Nix store is mounted in the guest
-because the file owner of the store paths typically don't match the
-owner of the QEMU process.
-
-After submitting a patch to the overlayfs mailing list[1], it turns out
-that my patch was incomplete[2] and needs a bit more rework.
-
-So instead of using an incomplete kernel patch in nixpkgs, which affects
-*all* users of overlayfs, not just NixOS VM tests, I decided that for
-now it's better to patch QEMU instead.
-
-The change here really only ignores the O_NOATIME flag so that the
-behaviour is similar to what NFS does. From open(2):
-
-This flag may not be effective on all filesystems. One example is NFS,
-where the server maintains the access time.
-
-This change is therefore only temporary until the final fix lands in the
-stable kernel releases.
-
-[1]: https://www.spinics.net/lists/linux-unionfs/msg06755.html
-[2]: https://www.spinics.net/lists/linux-unionfs/msg06756.html
-
-Signed-off-by: aszlig <aszlig@nix.build>
----
- hw/9pfs/9p.c | 1 -
- 1 file changed, 1 deletion(-)
-
-diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
-index a6d6b3f835..4eb26e2294 100644
---- a/hw/9pfs/9p.c
-+++ b/hw/9pfs/9p.c
-@@ -139,7 +139,6 @@ static int dotl_to_open_flags(int flags)
-         { P9_DOTL_DSYNC, O_DSYNC },
-         { P9_DOTL_FASYNC, FASYNC },
- #ifndef CONFIG_DARWIN
--        { P9_DOTL_NOATIME, O_NOATIME },
-         /*
-          *  On Darwin, we could map to F_NOCACHE, which is
-          *  similar, but doesn't quite have the same
--- 
-2.35.1
-

pkgs/applications/virtualization/qemu/default.nix

@@ -142,8 +142,6 @@ stdenv.mkDerivation rec {
     # set was removed during the process of upstreaming this functionality, and
     # will still be needed in nix until the macOS SDK reaches 10.13+.
     ./provide-fallback-for-utimensat.patch
-    # Still needed indefinitely
-    ./9p-ignore-noatime.patch
   ]
     ++ lib.optional nixosTestRunner ./force-uid0-on-9p.patch;