[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/adapter.go

@@ -0,0 +1,105 @@
+package sysfs
+
+import (
+	"fmt"
+	"io/fs"
+	"path"
+
+	experimentalsys "github.com/tetratelabs/wazero/experimental/sys"
+	"github.com/tetratelabs/wazero/sys"
+)
+
+type AdaptFS struct {
+	FS fs.FS
+}
+
+// String implements fmt.Stringer
+func (a *AdaptFS) String() string {
+	return fmt.Sprintf("%v", a.FS)
+}
+
+// OpenFile implements the same method as documented on sys.FS
+func (a *AdaptFS) OpenFile(path string, flag experimentalsys.Oflag, perm fs.FileMode) (experimentalsys.File, experimentalsys.Errno) {
+	return OpenFSFile(a.FS, cleanPath(path), flag, perm)
+}
+
+// Lstat implements the same method as documented on sys.FS
+func (a *AdaptFS) Lstat(path string) (sys.Stat_t, experimentalsys.Errno) {
+	// At this time, we make the assumption sys.FS instances do not support
+	// symbolic links, therefore Lstat is the same as Stat. This is obviously
+	// not true, but until FS.FS has a solid story for how to handle symlinks,
+	// we are better off not making a decision that would be difficult to
+	// revert later on.
+	//
+	// For further discussions on the topic, see:
+	// https://github.com/golang/go/issues/49580
+	return a.Stat(path)
+}
+
+// Stat implements the same method as documented on sys.FS
+func (a *AdaptFS) Stat(path string) (sys.Stat_t, experimentalsys.Errno) {
+	f, errno := a.OpenFile(path, experimentalsys.O_RDONLY, 0)
+	if errno != 0 {
+		return sys.Stat_t{}, errno
+	}
+	defer f.Close()
+	return f.Stat()
+}
+
+// Readlink implements the same method as documented on sys.FS
+func (a *AdaptFS) Readlink(string) (string, experimentalsys.Errno) {
+	return "", experimentalsys.ENOSYS
+}
+
+// Mkdir implements the same method as documented on sys.FS
+func (a *AdaptFS) Mkdir(string, fs.FileMode) experimentalsys.Errno {
+	return experimentalsys.ENOSYS
+}
+
+// Chmod implements the same method as documented on sys.FS
+func (a *AdaptFS) Chmod(string, fs.FileMode) experimentalsys.Errno {
+	return experimentalsys.ENOSYS
+}
+
+// Rename implements the same method as documented on sys.FS
+func (a *AdaptFS) Rename(string, string) experimentalsys.Errno {
+	return experimentalsys.ENOSYS
+}
+
+// Rmdir implements the same method as documented on sys.FS
+func (a *AdaptFS) Rmdir(string) experimentalsys.Errno {
+	return experimentalsys.ENOSYS
+}
+
+// Link implements the same method as documented on sys.FS
+func (a *AdaptFS) Link(string, string) experimentalsys.Errno {
+	return experimentalsys.ENOSYS
+}
+
+// Symlink implements the same method as documented on sys.FS
+func (a *AdaptFS) Symlink(string, string) experimentalsys.Errno {
+	return experimentalsys.ENOSYS
+}
+
+// Unlink implements the same method as documented on sys.FS
+func (a *AdaptFS) Unlink(string) experimentalsys.Errno {
+	return experimentalsys.ENOSYS
+}
+
+// Utimens implements the same method as documented on sys.FS
+func (a *AdaptFS) Utimens(string, int64, int64) experimentalsys.Errno {
+	return experimentalsys.ENOSYS
+}
+
+func cleanPath(name string) string {
+	if len(name) == 0 {
+		return name
+	}
+	// fs.ValidFile cannot be rooted (start with '/')
+	cleaned := name
+	if name[0] == '/' {
+		cleaned = name[1:]
+	}
+	cleaned = path.Clean(cleaned) // e.g. "sub/." -> "sub"
+	return cleaned
+}