gpt-utils: Drop -Wno-unused-variable and address one warning.

hardware/qcom/msm8998/gpt-utils/gpt-utils.cpp:750:17: error: unused variable 'ufs_dir_stat' [-Werror,-Wunused-variable]
    struct stat ufs_dir_stat;
                ^
hardware/qcom/msm8998/gpt-utils/gpt-utils.cpp:973:13: error: unused variable 'r' [-Werror,-Wunused-variable]
        int r, fd;
            ^
hardware/qcom/msm8998/gpt-utils/gpt-utils.cpp:973:16: error: unused variable 'fd' [-Werror,-Wunused-variable]
        int r, fd;
               ^
3 errors generated.

[ 22% 4/18] target  C++: libgptutils <= hardware/qcom/msm8998/gpt-utils/gpt-utils.cpp
In file included from hardware/qcom/msm8998/gpt-utils/gpt-utils.cpp:54:
system/core/libcutils/include_vndk/cutils/log.h:38:2: warning: "Deprecated: don't include cutils/log.h, use either android/log.h or log/log.h" [-W#warnings]
 ^
1 warning generated.

Test: lunch aosp_walleye-userdebug && m -j libgptutils
Change-Id: Ie3c33cc61fc62ac93ab0954a9e292b62cfcf9e03

recovery/gpt-utils/Android.mk

@@ -16,7 +16,7 @@
 
 LOCAL_PATH := $(call my-dir)
 
-gpt_utils_common_cflags := -Wall -Werror -Wno-unused-variable
+gpt_utils_common_cflags := -Wall -Werror
 
 include $(CLEAR_VARS)
 LOCAL_SRC_FILES := gpt-utils.cpp

recovery/gpt-utils/gpt-utils.cpp

@@ -51,7 +51,7 @@
 #include <vector>
 #include <string>
 #define LOG_TAG "gpt-utils"
-#include <cutils/log.h>
+#include <log/log.h>
 #include <cutils/properties.h>
 #include "gpt-utils.h"
 #include <endian.h>
@@ -747,7 +747,6 @@ int prepare_partitions(enum boot_update_stage stage, const char *dev_path)
     enum gpt_state gpt_prim, gpt_second;
     enum boot_update_stage internal_stage;
     struct stat xbl_partition_stat;
-    struct stat ufs_dir_stat;
 
     if (!dev_path) {
         fprintf(stderr, "%s: Invalid dev_path\n",
@@ -970,7 +969,6 @@ int add_lun_to_update_list(char *lun_path, struct update_data *dat)
 
 int prepare_boot_update(enum boot_update_stage stage)
 {
-        int r, fd;
         int is_ufs = gpt_utils_is_ufs_device();
         struct stat ufs_dir_stat;
         struct update_data data;