std.debug: watchOS: fixes for ilp32 ABI (#21765)

Xcode requires target arm64_32 (aarch64-watchos-ilp32) in order to
build code for Apple Watches. This commit fixes compilation errors
that appear when compiling with that target.

lib/std/debug.zig

@@ -656,7 +656,7 @@ pub const StackIterator = struct {
         // The implementation of DWARF unwinding on aarch64-macos is not complete. However, Apple mandates that
         // the frame pointer register is always used, so on this platform we can safely use the FP-based unwinder.
         if (builtin.target.isDarwin() and native_arch == .aarch64)
-            return init(first_address, context.mcontext.ss.fp);
+            return init(first_address, @truncate(context.mcontext.ss.fp));
 
         if (SelfInfo.supports_unwinding) {
             var iterator = init(first_address, null);

lib/std/debug/SelfInfo.zig

@@ -184,10 +184,12 @@ fn lookupModuleDyld(self: *SelfInfo, address: usize) !*Module {
                     }
 
                     for (cmd.getSections()) |sect| {
+                        const sect_addr: usize = @intCast(sect.addr);
+                        const sect_size: usize = @intCast(sect.size);
                         if (mem.eql(u8, "__unwind_info", sect.sectName())) {
-                            unwind_info = @as([*]const u8, @ptrFromInt(sect.addr + vmaddr_slide))[0..sect.size];
+                            unwind_info = @as([*]const u8, @ptrFromInt(sect_addr + vmaddr_slide))[0..sect_size];
                         } else if (mem.eql(u8, "__eh_frame", sect.sectName())) {
-                            eh_frame = @as([*]const u8, @ptrFromInt(sect.addr + vmaddr_slide))[0..sect.size];
+                            eh_frame = @as([*]const u8, @ptrFromInt(sect_addr + vmaddr_slide))[0..sect_size];
                         }
                     }
 
@@ -590,7 +592,7 @@ pub const Module = switch (native_os) {
                 const section_bytes = try Dwarf.chopSlice(mapped_mem, sect.offset, sect.size);
                 sections[section_index.?] = .{
                     .data = section_bytes,
-                    .virtual_address = sect.addr,
+                    .virtual_address = @intCast(sect.addr),
                     .owned = false,
                 };
             }