adbd: respect ADB_TRACE on host adbd.

Test: ADB_TRACE=1 adbd
Change-Id: I7cebbf7596add865fab95f5d6c746c0b8a16997a
diff --git a/adb/adb_trace.cpp b/adb/adb_trace.cpp
index c579dde..210241c 100644
--- a/adb/adb_trace.cpp
+++ b/adb/adb_trace.cpp
@@ -90,7 +90,7 @@
 int adb_trace_mask;
 
 std::string get_trace_setting() {
-#if ADB_HOST
+#if ADB_HOST || !defined(__ANDROID__)
     const char* setting = getenv("ADB_TRACE");
     if (setting == nullptr) {
         setting = "";