[hex] Use libhex to encode hex string in avmd and apexutil

Bug: 239413416
Test: atest avmdtool_tests libapexutil_rust.test
Change-Id: I58fcc32f62bea1cd34b171ac336a1ed13f5735b8
diff --git a/libs/apexutil/Android.bp b/libs/apexutil/Android.bp
index 3bdfc5f..4a4a673 100644
--- a/libs/apexutil/Android.bp
+++ b/libs/apexutil/Android.bp
@@ -27,6 +27,9 @@
     prefer_rlib: true,
     test_suites: ["general-tests"],
     data: ["tests/data/*"],
+    rustlibs: [
+        "libhex",
+    ],
     target: {
         host: {
             // TODO(b/204562227): remove once the build does this automatically