fix(overlays): exclude failing x86-64-v3 tests

Skip the flaky GnuTLS UDP readiness test and the SciPy FFT tests whose
precision differences are acceptable for our workloads.

common/global/nix.nix

@@ -31,6 +31,10 @@ in
         "flakes"
         "ca-derivations"
       ];
+      system-features = lib.mkAfter [
+        "gccarch-x86-64-v2"
+        "gccarch-x86-64-v3"
+      ];
       warn-dirty = false;
       flake-registry = ""; # disable global flake registries
       connect-timeout = 10;

python/installer/__main__.py

@@ -176,6 +176,21 @@ def create_zfs_datasets() -> None:
     run_output(("zfs", "create", "root_pool/home"))
     run_output(("zfs", "create", "-o", "reservation=1G", "root_pool/var"))
     run_output(("zfs", "create", "-o", "compression=zstd-9", "-o", "reservation=10G", "root_pool/nix"))
+    run_output(
+        (
+            "zfs",
+            "create",
+            "-o",
+            "sync=disabled",
+            "-o",
+            "redundant_metadata=some",
+            "-o",
+            "normalization=none",
+            "-o",
+            "utf8only=off",
+            "root_pool/nix_build",
+        )
+    )
     datasets = run_output(("zfs", "list", "-o", "name"))
 
     expected_datasets = {
@@ -183,6 +198,7 @@ def create_zfs_datasets() -> None:
         "root_pool/home",
         "root_pool/var",
         "root_pool/nix",
+        "root_pool/nix_build",
     }
     missing_datasets = expected_datasets.difference(datasets.splitlines())
     if missing_datasets:
@@ -248,6 +264,7 @@ def create_nix_hardware_file(mnt_dir: str, disks: Sequence[str], encrypt: str |
         '    "/home" = {\n      device = "root_pool/home";\n      fsType = "zfs";\n    };\n\n'
         '    "/var" = {\n      device = "root_pool/var";\n      fsType = "zfs";\n    };\n\n'
         '    "/nix" = {\n      device = "root_pool/nix";\n      fsType = "zfs";\n    };\n\n'
+        '    "/nix/var/nix/builds" = {\n      device = "root_pool/nix_build";\n      fsType = "zfs";\n    };\n\n'
         '    "/boot" = {\n'
         f'      device = "/dev/disk/by-uuid/{get_boot_drive_id(disks[0])}";\n'
         '      fsType = "vfat";\n      options = [\n        "fmask=0077"\n'
@@ -270,6 +287,7 @@ def install_nixos(mnt_dir: str, disks: Sequence[str], encrypt: str | None) -> No
     run_output(("mount", "-o", "X-mount.mkdir", "-t", "zfs", "root_pool/home", f"{mnt_dir}/home"))
     run_output(("mount", "-o", "X-mount.mkdir", "-t", "zfs", "root_pool/var", f"{mnt_dir}/var"))
     run_output(("mount", "-o", "X-mount.mkdir", "-t", "zfs", "root_pool/nix", f"{mnt_dir}/nix"))
+    run_output(("mount", "-o", "X-mount.mkdir", "-t", "zfs", "root_pool/nix_build", f"{mnt_dir}/nix/var/nix/builds"))
 
     for disk in disks:
         run_output(("mkfs.vfat", "-n", "EFI", f"{disk}-part1"))

systems/bob/hardware.nix

@@ -50,6 +50,11 @@
       fsType = "zfs";
     };
 
+    "/nix/var/nix/builds" = {
+      device = "root_pool/nix_build";
+      fsType = "zfs";
+    };
+
     "/var" = {
       device = "root_pool/var";
       fsType = "zfs";

systems/brain/hardware.nix

@@ -53,6 +53,11 @@
       fsType = "zfs";
     };
 
+    "/nix/var/nix/builds" = {
+      device = "root_pool/nix_build";
+      fsType = "zfs";
+    };
+
     "/boot" = {
       device = "/dev/disk/by-uuid/12CE-A600";
       fsType = "vfat";

systems/jeeves/default.nix

@@ -25,10 +25,6 @@ in
     ./runners
     ./syncthing.nix
   ];
-  nix.settings.system-features = lib.mkAfter [
-    "gccarch-x86-64-v2"
-    "gccarch-x86-64-v3"
-  ];
 
   services = {
     openssh.ports = [ 629 ];

systems/jeeves/hardware.nix

@@ -96,6 +96,11 @@ in
       fsType = "zfs";
     };
 
+    "/nix/var/nix/builds" = {
+      device = "root_pool/nix_build";
+      fsType = "zfs";
+    };
+
     "/var" = {
       device = "root_pool/var";
       fsType = "zfs";

systems/rhapsody-in-green/hardware.nix

@@ -34,14 +34,22 @@
       device = "root_pool/root";
       fsType = "zfs";
     };
+
     "/home" = {
       device = "root_pool/home";
       fsType = "zfs";
     };
+
+    "/nix/var/nix/builds" = {
+      device = "root_pool/nix_build";
+      fsType = "zfs";
+    };
+
     "/var" = {
       device = "root_pool/var";
       fsType = "zfs";
     };
+
     "/boot" = {
       device = "/dev/disk/by-uuid/12CE-A600";
       fsType = "vfat";