Zig workaround: don't use packed structs larger than 128 bits.

deps/zig/codegen/x86_64.zig

@@ -176,19 +176,21 @@ pub const Encoder = struct {
 
     /// Directly write a number to the code array with big endianness
     pub fn writeIntBig(self: Self, comptime T: type, value: T) void {
-        mem.writeIntBig(
+        mem.writeInt(
             T,
             self.code.addManyAsArrayAssumeCapacity(@divExact(@typeInfo(T).Int.bits, 8)),
             value,
+            .big,
         );
     }
 
     /// Directly write a number to the code array with little endianness
     pub fn writeIntLittle(self: Self, comptime T: type, value: T) void {
-        mem.writeIntLittle(
+        mem.writeInt(
             T,
             self.code.addManyAsArrayAssumeCapacity(@divExact(@typeInfo(T).Int.bits, 8)),
             value,
+            .little,
         );
     }
 

src/Compilation.zig

@@ -404,7 +404,7 @@ pub fn generateBuiltinMacros(comp: *Compilation) !Source {
         \\#define __ORDER_PDP_ENDIAN__ 3412
         \\
     );
-    if (comp.target.cpu.arch.endian() == .Little) try w.writeAll(
+    if (comp.target.cpu.arch.endian() == .little) try w.writeAll(
         \\#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__
         \\#define __LITTLE_ENDIAN__ 1
         \\

src/Diagnostics.zig

@@ -70,10 +70,9 @@ pub const Message = struct {
 
 pub const Tag = std.meta.DeclEnum(messages);
 
-// u4 to avoid any possible packed struct issues
-pub const Kind = enum(u4) { @"fatal error", @"error", note, warning, off, default };
+pub const Kind = enum { @"fatal error", @"error", note, warning, off, default };
 
-pub const Options = packed struct {
+pub const Options = struct {
     // do not directly use these, instead add `const NAME = true;`
     all: Kind = .default,
     extra: Kind = .default,

src/object/Elf.zig

@@ -20,7 +20,7 @@ const Symbol = struct {
     info: u8,
 };
 
-const Relocation = packed struct {
+const Relocation = struct {
     symbol: *Symbol,
     addend: i64,
     offset: u48,

src/target.zig

@@ -397,8 +397,8 @@ pub fn ldEmulationOption(target: std.Target, arm_endianness: ?std.builtin.Endian
         .thumb,
         .thumbeb,
         => switch (arm_endianness orelse target.cpu.arch.endian()) {
-            .Little => "armelf_linux_eabi",
-            .Big => "armelfb_linux_eabi",
+            .little => "armelf_linux_eabi",
+            .big => "armelfb_linux_eabi",
         },
         .aarch64 => "aarch64linux",
         .aarch64_be => "aarch64linuxb",