Add build tag to enable OSTRACE() logging

This commit adds the `sqlite_os_trace` build tag which sets the
`SQLITE_FORCE_OS_TRACE` and `SQLITE_DEBUG_OS_TRACE` compilation
flags. This produces verbose debugging output of every operating
system call made by SQLite.

sqlite3_opt_os_trace.go

@@ -0,0 +1,15 @@
+// Copyright (C) 2022 Yasuhiro Matsumoto <mattn.jp@gmail.com>.
+//
+// Use of this source code is governed by an MIT-style
+// license that can be found in the LICENSE file.
+
+//go:build sqlite_os_trace
+// +build sqlite_os_trace
+
+package sqlite3
+
+/*
+#cgo CFLAGS: -DSQLITE_FORCE_OS_TRACE=1
+#cgo CFLAGS: -DSQLITE_DEBUG_OS_TRACE=1
+*/
+import "C"