adb: don't use <error.h>.

This should fix the bloody Mac build, which doesn't have <error.h>. Since
we weren't entirely happy with error(3) anyway, switch to the toybox
style of error_exit and perror_exit, which are slightly briefer and quite
a bit more intention-revealing.

Bug: N/A
Test: builds
Change-Id: Ic8e411906c363af51657da5ce947b25a0b6bb1f3
diff --git a/adb/adb_utils.h b/adb/adb_utils.h
index 442ca2b..6d12225 100644
--- a/adb/adb_utils.h
+++ b/adb/adb_utils.h
@@ -14,8 +14,7 @@
  * limitations under the License.
  */
 
-#ifndef _ADB_UTILS_H_
-#define _ADB_UTILS_H_
+#pragma once
 
 #include <condition_variable>
 #include <mutex>
@@ -47,9 +46,12 @@
 
 std::string perror_str(const char* msg);
 
+[[noreturn]] void error_exit(const char* fmt, ...) __attribute__((__format__(__printf__, 1, 2)));
+[[noreturn]] void perror_exit(const char* fmt, ...) __attribute__((__format__(__printf__, 1, 2)));
+
 bool set_file_block_mode(int fd, bool block);
 
-extern int adb_close(int fd);
+int adb_close(int fd);
 
 // Given forward/reverse targets, returns true if they look sane. If an error is found, fills
 // |error| and returns false.
@@ -92,5 +94,3 @@
 };
 
 std::string GetLogFilePath();
-
-#endif