adbd: allow port configuration on host.

Test: manual
Change-Id: I68cbd9bdb253a68463cc65e63a764ad4fa410c1c
diff --git a/adb/daemon/main.cpp b/adb/daemon/main.cpp
index e5a4917..9ebab74 100644
--- a/adb/daemon/main.cpp
+++ b/adb/daemon/main.cpp
@@ -248,6 +248,12 @@
         prop_port = android::base::GetProperty("persist.adb.tcp.port", "");
     }
 
+#if !defined(__ANDROID__)
+    if (prop_port.empty() && getenv("ADBD_PORT")) {
+        prop_port = getenv("ADBD_PORT");
+    }
+#endif
+
     int port;
     if (sscanf(prop_port.c_str(), "%d", &port) == 1 && port > 0) {
         D("using port=%d", port);