Add mDNS device discovery for adb client

Test: Was able to discover a raspberry pi.
Bug: 28074466
(cherry picked from e292cd16760321fccc99c8c261cb92fa4b6462ab)

Change-Id: Id9571576457a4a0a078e48a274a4e8eac78bfe2b
diff --git a/adb/Android.mk b/adb/Android.mk
index d5b8ddb..ef29695 100644
--- a/adb/Android.mk
+++ b/adb/Android.mk
@@ -145,6 +145,7 @@
 LOCAL_SRC_FILES := \
     $(LIBADB_SRC_FILES) \
     adb_auth_host.cpp \
+    transport_mdns.cpp
 
 LOCAL_SRC_FILES_darwin := $(LIBADB_darwin_SRC_FILES)
 LOCAL_SRC_FILES_linux := $(LIBADB_linux_SRC_FILES)
@@ -154,7 +155,7 @@
 
 # Even though we're building a static library (and thus there's no link step for
 # this to take effect), this adds the includes to our path.
-LOCAL_STATIC_LIBRARIES := libcrypto_utils libcrypto libbase
+LOCAL_STATIC_LIBRARIES := libcrypto_utils libcrypto libbase libmdnssd
 LOCAL_STATIC_LIBRARIES_linux := libusb
 LOCAL_STATIC_LIBRARIES_darwin := libusb
 
@@ -225,6 +226,7 @@
     libcutils \
     libdiagnose_usb \
     libgmock_host \
+    libmdnssd \
 
 LOCAL_STATIC_LIBRARIES_linux := libusb
 LOCAL_STATIC_LIBRARIES_darwin := libusb
@@ -292,6 +294,7 @@
     libcrypto \
     libdiagnose_usb \
     liblog \
+    libmdnssd \
 
 # Don't use libcutils on Windows.
 LOCAL_STATIC_LIBRARIES_darwin := libcutils