vendor: update buildkit to v0.8

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

vendor/github.com/Microsoft/hcsshim/internal/winapi/utils.go

@@ -0,0 +1,60 @@
+package winapi
+
+import (
+	"errors"
+	"syscall"
+	"unicode/utf16"
+	"unsafe"
+)
+
+type UnicodeString struct {
+	Length        uint16
+	MaximumLength uint16
+	Buffer        *uint16
+}
+
+//String converts a UnicodeString to a golang string
+func (uni UnicodeString) String() string {
+	p := (*[0xffff]uint16)(unsafe.Pointer(uni.Buffer))
+
+	// UnicodeString is not guaranteed to be null terminated, therefore
+	// use the UnicodeString's Length field
+	lengthInChars := uni.Length / 2
+	return syscall.UTF16ToString(p[:lengthInChars])
+}
+
+// NewUnicodeString allocates a new UnicodeString and copies `s` into
+// the buffer of the new UnicodeString.
+func NewUnicodeString(s string) (*UnicodeString, error) {
+	ws := utf16.Encode(([]rune)(s))
+	if len(ws) > 32767 {
+		return nil, syscall.ENAMETOOLONG
+	}
+
+	uni := &UnicodeString{
+		Length:        uint16(len(ws) * 2),
+		MaximumLength: uint16(len(ws) * 2),
+		Buffer:        &make([]uint16, len(ws))[0],
+	}
+	copy((*[32768]uint16)(unsafe.Pointer(uni.Buffer))[:], ws)
+	return uni, nil
+}
+
+// ConvertStringSetToSlice is a helper function used to convert the contents of
+// `buf` into a string slice. `buf` contains a set of null terminated strings
+// with an additional null at the end to indicate the end of the set.
+func ConvertStringSetToSlice(buf []byte) ([]string, error) {
+	var results []string
+	prev := 0
+	for i := range buf {
+		if buf[i] == 0 {
+			if prev == i {
+				// found two null characters in a row, return result
+				return results, nil
+			}
+			results = append(results, string(buf[prev:i]))
+			prev = i + 1
+		}
+	}
+	return nil, errors.New("string set malformed: missing null terminator at end of buffer")
+}