adbd: compile for host.

Preparatory step for testing adb on GCE on non-linux hosts: instead of
pointing them at a device (emulated or otherwise), point them at adbd
running on a linux host instead.

Test: adbd & adb connect localhost:5555; adb -e wait-for-device shell
Change-Id: Ib22d51a4fc9e6e68f71bf1b3b9b2e1b0bd844760
diff --git a/adb/daemon/auth.cpp b/adb/daemon/auth.cpp
index 180df8f..1800f84 100644
--- a/adb/daemon/auth.cpp
+++ b/adb/daemon/auth.cpp
@@ -67,7 +67,7 @@
                 // b64_pton requires one additional byte in the target buffer for
                 // decoding to succeed. See http://b/28035006 for details.
                 uint8_t keybuf[ANDROID_PUBKEY_ENCODED_SIZE + 1];
-                if (__b64_pton(line.c_str(), keybuf, sizeof(keybuf)) != ANDROID_PUBKEY_ENCODED_SIZE) {
+                if (b64_pton(line.c_str(), keybuf, sizeof(keybuf)) != ANDROID_PUBKEY_ENCODED_SIZE) {
                     LOG(ERROR) << "Invalid base64 key " << line.c_str() << " in " << path;
                     continue;
                 }