tryFindProgram

fn tryFindProgram(b: *Build, full_path: []const u8) ?[]const u8 {
    const graph = b.graph;
    const io = graph.io;
    const arena = graph.arena;

    if (Io.Dir.cwd().access(io, full_path, .{ .execute = true })) |_| {
        return full_path;
    } else |err| switch (err) {
        error.FileNotFound, error.AccessDenied, error.PermissionDenied => |e| {
            if (graph.verbose) log.info("searched: {t} {s}", .{ e, full_path });
        },
        else => |e| return panic("failed accessing {s}: {t}", .{ full_path, e }),
    }

    if (builtin.os.tag == .windows) {
        if (b.graph.environ_map.get("PATHEXT")) |PATHEXT| {
            var it = mem.tokenizeScalar(u8, PATHEXT, fs.path.delimiter);

            const extended_path_buf = arena.alloc(u8, full_path.len + 1 + std.process.WindowsExtension.max_len) catch @panic("OOM");
            @memcpy(extended_path_buf[0..full_path.len], full_path);

            while (it.next()) |ext| {
                if (!supportedWindowsProgramExtension(ext)) continue;

                @memcpy(extended_path_buf[full_path.len..][0..ext.len], ext);
                const extended_path = extended_path_buf[0 .. full_path.len + ext.len];

                if (Io.Dir.cwd().access(io, extended_path, .{ .execute = true })) |_| {
                    return extended_path;
                } else |err| switch (err) {
                    error.FileNotFound, error.AccessDenied, error.PermissionDenied => |e| {
                        if (graph.verbose) log.info("searched: {t} {s}", .{ e, extended_path });
                    },
                    else => |e| return panic("failed accessing {s}: {t}", .{ extended_path, e }),
                }
            }
        }
    }

    return null;
}