Add folly certs/defs.bzl to shim

Summary:
X-link: pytorch/executorch#3851

We need to do this so that we can build fizz.
Context: https://fb.workplace.com/groups/3434452653448246/permalink/4069550066605165/

Reviewed By: bigfootjon

Differential Revision: D58163115

fbshipit-source-id: 2edcb5ed40d6b54c7d71255d06e73482b7f6d601

shim/folly/io/async/test/certs/defs.bzl

@@ -0,0 +1,16 @@
+load("@fbcode_macros//build_defs:native_rules.bzl", "alias")
+
+def alias_pem(pems: list[str]):
+    for pem in pems:
+        alias(
+            name = pem,
+            actual = "//folly/io/async/test/certs:{pem}".format(pem = pem),
+        )
+
+def alias_pem_for_xplat(pems: list[str]):
+    # in xplat these pem files are exported in //xplat/folly/io/async/test
+    for pem in pems:
+        alias(
+            name = pem,
+            actual = "//xplat/folly/io/async/test:certs/{pem}".format(pem = pem),
+        )