build: more Zig 0.15.2 updates (#9217)

- update nixpkgs now that Zig 0.15.2 is available in nixpkgs
- drop hack that worked around compile failures on systems with more
than 32 cores
- enforce patch version of Zig

build.zig

@@ -10,10 +10,6 @@ comptime {
 }
 
 pub fn build(b: *std.Build) !void {
-    // Works around a Zig but still present in 0.15.1. Remove when fixed.
-    // https://github.com/ghostty-org/ghostty/issues/8924
-    try limitCoresForZigBug();
-
     // This defines all the available build options (e.g. `-D`). If you
     // want to know what options are available, you can run `--help` or
     // you can read `src/build/Config.zig`.
@@ -312,13 +308,3 @@ pub fn build(b: *std.Build) !void {
         try translations_step.addError("cannot update translations when i18n is disabled", .{});
     }
 }
-
-// WARNING: Remove this when https://github.com/ghostty-org/ghostty/issues/8924 is resolved!
-// Limit ourselves to 32 cpus on Linux because of an upstream Zig bug.
-fn limitCoresForZigBug() !void {
-    if (comptime builtin.os.tag != .linux) return;
-    const pid = std.os.linux.getpid();
-    var set: std.bit_set.ArrayBitSet(usize, std.os.linux.CPU_SETSIZE * 8) = .initEmpty();
-    for (0..32) |cpu| set.set(cpu);
-    try std.os.linux.sched_setaffinity(pid, &set.masks);
-}