Use -Werror in frameworks/base

* Fix unused variable and return value warnings.

Bug: 66996870
Test: build with WITH_TIDY=1
Change-Id: I890e65a20848d00559ba5a4f9691be1347b456af
diff --git a/tools/bit/command.cpp b/tools/bit/command.cpp
index 9a8449b..1ff7c22 100644
--- a/tools/bit/command.cpp
+++ b/tools/bit/command.cpp
@@ -105,7 +105,9 @@
     }
 
     int fds[2];
-    pipe(fds);
+    if (0 != pipe(fds)) {
+        return string();
+    }
 
     pid_t pid = fork();