Suppress implicit-fallthrough warnings.

Add FALLTHROUGH_INTENDED for clang compiler.

Bug: 112564944
Test: build with global -Wimplicit-fallthrough.
Change-Id: I40f8bbf94e207c9dd90921e9b762ba51abab5777
diff --git a/libsysutils/src/SocketClient.cpp b/libsysutils/src/SocketClient.cpp
index 0625db7..fe2f3d6 100644
--- a/libsysutils/src/SocketClient.cpp
+++ b/libsysutils/src/SocketClient.cpp
@@ -27,6 +27,8 @@
 #include <sys/types.h>
 #include <unistd.h>
 
+#include <android-base/file.h>
+#include <android-base/macros.h>
 #include <log/log.h>
 #include <sysutils/SocketClient.h>
 
@@ -145,7 +147,8 @@
         switch (*arg) {
         case '\\':
         case '"':
-            *(current++) = '\\'; // fallthrough
+            *(current++) = '\\';
+            FALLTHROUGH_INTENDED;
         default:
             *(current++) = *(arg++);
         }