[open-dice] Add a local strlen implementation for open-dice

It requires strlen() in the cbor_writer library which is not included in
the OT development environment.

Bug: 356532759
Signed-off-by: Tommy Chiu <tommychiu@google.com>

third_party/open-dice/Add-a-local-strlen-implementation.patch

@@ -0,0 +1,39 @@
+From 1a2ead40e2e15ca058882ad86f4ac32e5c5b6177 Mon Sep 17 00:00:00 2001
+From: Tommy Chiu <tommychiu@google.com>
+Date: Thu, 17 Oct 2024 13:23:43 +0800
+Subject: [PATCH] Add a local strlen implementation
+
+Not all developing environments have access to strlen.
+---
+ src/cbor_writer.c | 8 +++++++-
+ 1 file changed, 7 insertions(+), 1 deletion(-)
+
+diff --git a/src/cbor_writer.c b/src/cbor_writer.c
+index 6c70129..c473543 100644
+--- a/src/cbor_writer.c
++++ b/src/cbor_writer.c
+@@ -30,6 +30,12 @@ enum CborType {
+   CBOR_TYPE_SIMPLE = 7,
+ };
+
++static unsigned long _strlen(const char* in) {
++  unsigned long ret;
++  for (ret = 0; *in++; ret++);
++  return ret;
++}
++
+ static bool CborWriteWouldOverflowCursor(size_t size, struct CborOut* out) {
+   return size > SIZE_MAX - out->cursor;
+ }
+@@ -127,7 +133,7 @@ uint8_t* CborAllocBstr(size_t data_size, struct CborOut* out) {
+ }
+
+ void CborWriteTstr(const char* str, struct CborOut* out) {
+-  CborWriteStr(CBOR_TYPE_TSTR, strlen(str), str, out);
++  CborWriteStr(CBOR_TYPE_TSTR, _strlen(str), str, out);
+ }
+
+ char* CborAllocTstr(size_t size, struct CborOut* out) {
+-- 
+2.47.0.rc1.288.g06298d1525-goog
+

third_party/open-dice/repos.bzl

@@ -12,4 +12,8 @@ def open_dice_repos(local = None):
         strip_prefix = "open-dice-cf3f4cc7a3506a33ee3a437544ef6f40056b3563",
         urls = ["https://github.com/google/open-dice/archive/cf3f4cc7a3506a33ee3a437544ef6f40056b3563.zip"],
         sha256 = "d7ce830111451afe2a255cac3b750f82e50efe2aaf6bac0b076881c964cfe78d",
+        patches = [
+            Label("//third_party/open-dice:Add-a-local-strlen-implementation.patch"),
+        ],
+        patch_args = ["-p1"],
     )