[experiment] add alternative wasm sqlite3 implementation available via build-tag (#2863)

This allows for building GoToSocial with [SQLite transpiled to WASM](https://github.com/ncruces/go-sqlite3) and accessed through [Wazero](https://wazero.io/).

vendor/github.com/tetratelabs/wazero/internal/sysfs/file_unix.go

@@ -0,0 +1,39 @@
+//go:build unix && !tinygo
+
+package sysfs
+
+import (
+	"syscall"
+
+	"github.com/tetratelabs/wazero/experimental/sys"
+)
+
+const (
+	nonBlockingFileReadSupported  = true
+	nonBlockingFileWriteSupported = true
+)
+
+func rmdir(path string) sys.Errno {
+	err := syscall.Rmdir(path)
+	return sys.UnwrapOSError(err)
+}
+
+// readFd exposes syscall.Read.
+func readFd(fd uintptr, buf []byte) (int, sys.Errno) {
+	if len(buf) == 0 {
+		return 0, 0 // Short-circuit 0-len reads.
+	}
+	n, err := syscall.Read(int(fd), buf)
+	errno := sys.UnwrapOSError(err)
+	return n, errno
+}
+
+// writeFd exposes syscall.Write.
+func writeFd(fd uintptr, buf []byte) (int, sys.Errno) {
+	if len(buf) == 0 {
+		return 0, 0 // Short-circuit 0-len writes.
+	}
+	n, err := syscall.Write(int(fd), buf)
+	errno := sys.UnwrapOSError(err)
+	return n, errno
+}