allow setting legacy boot flag on gpt disks

Author: Khitiara

src/BuildInterface.zig

@@ -155,6 +155,10 @@ const ContentWriter = struct {
             .gpt_part_table => |data| {
                 try cw.code.writeAll("gpt-part\n");
 
+                if(data.legacy_bootable) {
+                    try cw.code.writeAll("  legacy-bootable\n");
+                }
+
                 for (data.partitions) |part| {
                     try cw.code.writeAll("  part\n");
                     try cw.code.writeAll("    type ");
@@ -353,6 +357,7 @@ pub const MbrPartTable = struct {
 };
 
 pub const GptPartTable = struct {
+    legacy_bootable: bool = false,
     partitions: []const Partition,
 
     pub const Partition = struct {

src/components/part/GptPartitionTable.zig

@@ -7,6 +7,7 @@ const PartTable = @This();
 const block_size = 512; // TODO support other block sizes
 
 disk_id: ?Guid,
+legacy_bootable: bool = false,
 partitions: []Partition,
 
 pub fn parse(ctx: dim.Context) !dim.Content {
@@ -22,6 +23,7 @@ pub fn parse(ctx: dim.Context) !dim.Content {
             guid,
             part,
             endgpt,
+            @"legacy-bootable",
         });
         switch (kw) {
             .guid => {
@@ -33,6 +35,7 @@ pub fn parse(ctx: dim.Context) !dim.Content {
                     return ctx.report_fatal_error("Invalid disk GUID: {}", .{err});
             },
             .part => (try partitions.addOne()).* = try parsePartition(ctx),
+            .@"legacy-bootable" => pt.legacy_bootable = true,
             .endgpt => break :loop,
         }
     }
@@ -220,7 +223,7 @@ pub fn render(table: *PartTable, stream: *dim.BinaryStream) dim.Content.RenderEr
         .partitions = .{ .{
             .offset = block_size,
             .size = null,
-            .bootable = false,
+            .bootable = table.legacy_bootable,
             .type = 0xee,
             .contains = .empty,
         }, null, null, null },