[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/experimental/sys/errno.go

@@ -0,0 +1,98 @@
+package sys
+
+import "strconv"
+
+// Errno is a subset of POSIX errno used by wazero interfaces. Zero is not an
+// error. Other values should not be interpreted numerically, rather by constants
+// prefixed with 'E'.
+//
+// See https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/errno.h.html
+type Errno uint16
+
+// ^-- Note: This will eventually move to the public /sys package. It is
+// experimental until we audit the socket related APIs to ensure we have all
+// the Errno it returns, and we export fs.FS. This is not in /internal/sys as
+// that would introduce a package cycle.
+
+// This is a subset of errors to reduce implementation burden. `wasip1` defines
+// almost all POSIX error numbers, but not all are used in practice. wazero
+// will add ones needed in POSIX order, as needed by functions that explicitly
+// document returning them.
+//
+// https://github.com/WebAssembly/WASI/blob/snapshot-01/phases/snapshot/docs.md#-errno-enumu16
+const (
+	EACCES Errno = iota + 1
+	EAGAIN
+	EBADF
+	EEXIST
+	EFAULT
+	EINTR
+	EINVAL
+	EIO
+	EISDIR
+	ELOOP
+	ENAMETOOLONG
+	ENOENT
+	ENOSYS
+	ENOTDIR
+	ERANGE
+	ENOTEMPTY
+	ENOTSOCK
+	ENOTSUP
+	EPERM
+	EROFS
+
+	// NOTE ENOTCAPABLE is defined in wasip1, but not in POSIX. wasi-libc
+	// converts it to EBADF, ESPIPE or EINVAL depending on the call site.
+	// It isn't known if compilers who don't use ENOTCAPABLE would crash on it.
+)
+
+// Error implements error
+func (e Errno) Error() string {
+	switch e {
+	case 0: // not an error
+		return "success"
+	case EACCES:
+		return "permission denied"
+	case EAGAIN:
+		return "resource unavailable, try again"
+	case EBADF:
+		return "bad file descriptor"
+	case EEXIST:
+		return "file exists"
+	case EFAULT:
+		return "bad address"
+	case EINTR:
+		return "interrupted function"
+	case EINVAL:
+		return "invalid argument"
+	case EIO:
+		return "input/output error"
+	case EISDIR:
+		return "is a directory"
+	case ELOOP:
+		return "too many levels of symbolic links"
+	case ENAMETOOLONG:
+		return "filename too long"
+	case ENOENT:
+		return "no such file or directory"
+	case ENOSYS:
+		return "functionality not supported"
+	case ENOTDIR:
+		return "not a directory or a symbolic link to a directory"
+	case ERANGE:
+		return "result too large"
+	case ENOTEMPTY:
+		return "directory not empty"
+	case ENOTSOCK:
+		return "not a socket"
+	case ENOTSUP:
+		return "not supported (may be the same value as [EOPNOTSUPP])"
+	case EPERM:
+		return "operation not permitted"
+	case EROFS:
+		return "read-only file system"
+	default:
+		return "Errno(" + strconv.Itoa(int(e)) + ")"
+	}
+}