Re-vendor, and use mtrmac/image-spec:id-based-loader to fix tests

Anyone running (vndr) currently ends up with failing tests in OCI schema
validation because gojsonschema has fixed its "$ref" interpretation, exposing
inconsistent URI usage inside image-spec/schema.

So, this runs (vndr), and uses mtrmac/image-spec:id-based-loader
( https://github.com/opencontainers/image-spec/pull/739 ) to make the tests pass
again.  As soon as that PR is merged we should revert to using the upstream
image-spec repo again.

vendor/golang.org/x/sys/unix/syscall_dragonfly.go

@@ -14,6 +14,7 @@ package unix
 
 import "unsafe"
 
+// SockaddrDatalink implements the Sockaddr interface for AF_LINK type sockets.
 type SockaddrDatalink struct {
 	Len    uint8
 	Family uint8
@@ -56,22 +57,6 @@ func nametomib(name string) (mib []_C_int, err error) {
 	return buf[0 : n/siz], nil
 }
 
-func direntIno(buf []byte) (uint64, bool) {
-	return readInt(buf, unsafe.Offsetof(Dirent{}.Fileno), unsafe.Sizeof(Dirent{}.Fileno))
-}
-
-func direntReclen(buf []byte) (uint64, bool) {
-	namlen, ok := direntNamlen(buf)
-	if !ok {
-		return 0, false
-	}
-	return (16 + namlen + 1 + 7) &^ 7, true
-}
-
-func direntNamlen(buf []byte) (uint64, bool) {
-	return readInt(buf, unsafe.Offsetof(Dirent{}.Namlen), unsafe.Sizeof(Dirent{}.Namlen))
-}
-
 //sysnb pipe() (r int, w int, err error)
 
 func Pipe(p []int) (err error) {
@@ -110,6 +95,23 @@ func Accept4(fd, flags int) (nfd int, sa Sockaddr, err error) {
 	return
 }
 
+const ImplementsGetwd = true
+
+//sys	Getcwd(buf []byte) (n int, err error) = SYS___GETCWD
+
+func Getwd() (string, error) {
+	var buf [PathMax]byte
+	_, err := Getcwd(buf[0:])
+	if err != nil {
+		return "", err
+	}
+	n := clen(buf[:])
+	if n < 1 {
+		return "", EINVAL
+	}
+	return string(buf[:n]), nil
+}
+
 func Getfsstat(buf []Statfs_t, flags int) (n int, err error) {
 	var _p0 unsafe.Pointer
 	var bufsize uintptr
@@ -169,6 +171,69 @@ func IoctlGetTermios(fd int, req uint) (*Termios, error) {
 	return &value, err
 }
 
+func sysctlUname(mib []_C_int, old *byte, oldlen *uintptr) error {
+	err := sysctl(mib, old, oldlen, nil, 0)
+	if err != nil {
+		// Utsname members on Dragonfly are only 32 bytes and
+		// the syscall returns ENOMEM in case the actual value
+		// is longer.
+		if err == ENOMEM {
+			err = nil
+		}
+	}
+	return err
+}
+
+func Uname(uname *Utsname) error {
+	mib := []_C_int{CTL_KERN, KERN_OSTYPE}
+	n := unsafe.Sizeof(uname.Sysname)
+	if err := sysctlUname(mib, &uname.Sysname[0], &n); err != nil {
+		return err
+	}
+	uname.Sysname[unsafe.Sizeof(uname.Sysname)-1] = 0
+
+	mib = []_C_int{CTL_KERN, KERN_HOSTNAME}
+	n = unsafe.Sizeof(uname.Nodename)
+	if err := sysctlUname(mib, &uname.Nodename[0], &n); err != nil {
+		return err
+	}
+	uname.Nodename[unsafe.Sizeof(uname.Nodename)-1] = 0
+
+	mib = []_C_int{CTL_KERN, KERN_OSRELEASE}
+	n = unsafe.Sizeof(uname.Release)
+	if err := sysctlUname(mib, &uname.Release[0], &n); err != nil {
+		return err
+	}
+	uname.Release[unsafe.Sizeof(uname.Release)-1] = 0
+
+	mib = []_C_int{CTL_KERN, KERN_VERSION}
+	n = unsafe.Sizeof(uname.Version)
+	if err := sysctlUname(mib, &uname.Version[0], &n); err != nil {
+		return err
+	}
+
+	// The version might have newlines or tabs in it, convert them to
+	// spaces.
+	for i, b := range uname.Version {
+		if b == '\n' || b == '\t' {
+			if i == len(uname.Version)-1 {
+				uname.Version[i] = 0
+			} else {
+				uname.Version[i] = ' '
+			}
+		}
+	}
+
+	mib = []_C_int{CTL_HW, HW_MACHINE}
+	n = unsafe.Sizeof(uname.Machine)
+	if err := sysctlUname(mib, &uname.Machine[0], &n); err != nil {
+		return err
+	}
+	uname.Machine[unsafe.Sizeof(uname.Machine)-1] = 0
+
+	return nil
+}
+
 /*
  * Exposed directly
  */