Use -Werror in external/drm_hwcomposer

* Suppress non-critical warnings.

Bug: 66996870
Test: build with WITH_TIDY=1
Exempt-From-Owner-Approval: Fix broken builds
Change-Id: Icd412ef21c074ecea91eb91508703e42317a2b4b
diff --git a/Android.mk b/Android.mk
index c5ccd36..44ab1bb 100644
--- a/Android.mk
+++ b/Android.mk
@@ -16,6 +16,15 @@
 
 LOCAL_PATH := $(call my-dir)
 
+common_drm_hwcomposer_cflags := \
+    -Wall \
+    -Werror \
+    -Wno-unused-function \
+    -Wno-unused-label \
+    -Wno-unused-parameter \
+    -Wno-unused-private-field \
+    -Wno-unused-variable \
+
 # =====================
 # libdrmhwc_utils.a
 # =====================
@@ -24,6 +33,8 @@
 LOCAL_SRC_FILES := \
 	worker.cpp
 
+LOCAL_CFLAGS := $(common_drm_hwcomposer_cflags)
+
 LOCAL_MODULE := libdrmhwc_utils
 
 include $(BUILD_STATIC_LIBRARY)
@@ -75,6 +86,8 @@
 	virtualcompositorworker.cpp \
 	vsyncworker.cpp
 
+LOCAL_CFLAGS := $(common_drm_hwcomposer_cflags)
+
 LOCAL_CPPFLAGS += \
 	-DHWC2_USE_CPP11 \
 	-DHWC2_INCLUDE_STRINGIFICATION