Fix Win32 adb build (for the second time today).

Change-Id: I83cb407660cd8b5ed65a80574875fe261e8a8926
diff --git a/adb/Android.mk b/adb/Android.mk
index 4f75b43..355bb7f 100644
--- a/adb/Android.mk
+++ b/adb/Android.mk
@@ -47,8 +47,12 @@
 LIBADB_CFLAGS := \
     $(ADB_COMMON_CFLAGS) \
     -fvisibility=hidden \
+
+LIBADB_linux_CFLAGS := \
     -std=c++14 \
 
+LIBADB_CFLAGS += $(LIBADB_$(HOST_OS)_CFLAGS)
+
 LIBADB_darwin_SRC_FILES := \
     fdevent.cpp \
     get_my_path_darwin.cpp \