Suppress ThreadNetwork HAL debug log on user build

Due to security concerns, ThreadNetwork HAL service's debug log should
not be visible on user builds.

The "debuggable" field defines the flags that will be applied to
userdebug/eng variant builds.

Bug: 359338609
Test: No debug log from android.hardware.threadnetwork-service in logcat
Change-Id: I13993191efd3841fc8db1888be7c59c86f6608d3
diff --git a/threadnetwork/aidl/default/Android.bp b/threadnetwork/aidl/default/Android.bp
index 51e5c25..a840fa3 100644
--- a/threadnetwork/aidl/default/Android.bp
+++ b/threadnetwork/aidl/default/Android.bp
@@ -14,6 +14,8 @@
     vendor: true,
     relative_install_path: "hw",
 
+    defaults: ["android.hardware.threadnetwork-service.defaults"],
+
     shared_libs: [
         "libbinder_ndk",
         "liblog",
@@ -43,6 +45,17 @@
     ],
 }
 
+cc_defaults {
+    name: "android.hardware.threadnetwork-service.defaults",
+    product_variables: {
+        debuggable: {
+            cppflags: [
+                "-DDEV_BUILD",
+            ],
+        },
+    },
+}
+
 cc_fuzz {
     name: "android.hardware.threadnetwork-service.fuzzer",
 
diff --git a/threadnetwork/aidl/default/utils.cpp b/threadnetwork/aidl/default/utils.cpp
index 3552b3a..740f331 100644
--- a/threadnetwork/aidl/default/utils.cpp
+++ b/threadnetwork/aidl/default/utils.cpp
@@ -43,6 +43,7 @@
 }
 
 void otDumpDebgPlat(const char* aText, const void* aData, uint16_t aDataLength) {
+#ifdef DEV_BUILD
     constexpr uint16_t kBufSize = 512;
     char buf[kBufSize];
 
@@ -55,6 +56,11 @@
 
         __android_log_print(ANDROID_LOG_DEBUG, LOG_TAG, "%s: %s", aText, buf);
     }
+#else
+    OT_UNUSED_VARIABLE(aText);
+    OT_UNUSED_VARIABLE(aData);
+    OT_UNUSED_VARIABLE(aDataLength);
+#endif
 }
 
 OT_TOOL_WEAK void otPlatAlarmMilliFired(otInstance* aInstance) {