Use -Werror in system/core

* Move -Wall -Werror from cppflags to cflags.
* Fix/suppress warning on unused variables.

Bug: 66996870
Test: build with WITH_TIDY=1
Change-Id: I1e05e96a1d0bcb2ccef1ce456504b3af57167cc5
diff --git a/libutils/Android.bp b/libutils/Android.bp
index b70845b..4bd2a98 100644
--- a/libutils/Android.bp
+++ b/libutils/Android.bp
@@ -75,7 +75,7 @@
         "misc.cpp",
     ],
 
-    cflags: ["-Werror"],
+    cflags: ["-Wall", "-Werror"],
     include_dirs: ["external/safe-iop/include"],
     header_libs: [
         "libutils_headers",
@@ -154,6 +154,7 @@
     static_libs: ["libutils"],
     shared_libs: ["liblog"],
     srcs: ["SharedBufferTest.cpp"],
+    cflags: ["-Wall", "-Werror"],
 }
 
 subdirs = ["tests"]
diff --git a/libutils/RefBase.cpp b/libutils/RefBase.cpp
index f5f881f..8bccb0f 100644
--- a/libutils/RefBase.cpp
+++ b/libutils/RefBase.cpp
@@ -410,8 +410,7 @@
         return;
     }
 
-    int32_t old = refs->mStrong.fetch_sub(INITIAL_STRONG_VALUE,
-            std::memory_order_relaxed);
+    int32_t old __unused = refs->mStrong.fetch_sub(INITIAL_STRONG_VALUE, std::memory_order_relaxed);
     // A decStrong() must still happen after us.
     ALOG_ASSERT(old > INITIAL_STRONG_VALUE, "0x%x too small", old);
     refs->mBase->onFirstRef();
diff --git a/libutils/StopWatch.cpp b/libutils/StopWatch.cpp
index 219c13c..d01865e 100644
--- a/libutils/StopWatch.cpp
+++ b/libutils/StopWatch.cpp
@@ -30,10 +30,7 @@
 
 namespace android {
 
-
-StopWatch::StopWatch(const char *name, int clock, uint32_t flags)
-    :   mName(name), mClock(clock), mFlags(flags)
-{
+StopWatch::StopWatch(const char* name, int clock) : mName(name), mClock(clock) {
     reset();
 }
 
diff --git a/libutils/include/utils/StopWatch.h b/libutils/include/utils/StopWatch.h
index 693dd3c..76d78d0 100644
--- a/libutils/include/utils/StopWatch.h
+++ b/libutils/include/utils/StopWatch.h
@@ -29,21 +29,18 @@
 class StopWatch
 {
 public:
-        StopWatch(  const char *name,
-                    int clock = SYSTEM_TIME_MONOTONIC,
-                    uint32_t flags = 0);
-        ~StopWatch();
-        
-        const char* name() const;
-        nsecs_t     lap();
-        nsecs_t     elapsedTime() const;
+  StopWatch(const char* name, int clock = SYSTEM_TIME_MONOTONIC);
+  ~StopWatch();
 
-        void        reset();
-        
+  const char* name() const;
+  nsecs_t lap();
+  nsecs_t elapsedTime() const;
+
+  void reset();
+
 private:
     const char*     mName;
     int             mClock;
-    uint32_t        mFlags;
     
     struct lap_t {
         nsecs_t     soFar;
diff --git a/libutils/tests/Android.bp b/libutils/tests/Android.bp
index a891fca..a3e7ffe 100644
--- a/libutils/tests/Android.bp
+++ b/libutils/tests/Android.bp
@@ -77,6 +77,7 @@
     host_supported: true,
     relative_install_path: "libutils_tests",
     srcs: ["Singleton_test1.cpp"],
+    cflags: ["-Wall", "-Werror"],
 }
 
 cc_test_library {
@@ -84,5 +85,6 @@
     host_supported: true,
     relative_install_path: "libutils_tests",
     srcs: ["Singleton_test2.cpp"],
+    cflags: ["-Wall", "-Werror"],
     shared_libs: ["libutils_tests_singleton1"],
 }