vendor: update buildkit to 2943a0838

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

vendor/golang.org/x/crypto/ssh/terminal/terminal.go

@@ -113,6 +113,7 @@ func NewTerminal(c io.ReadWriter, prompt string) *Terminal {
 }
 
 const (
+	keyCtrlC     = 3
 	keyCtrlD     = 4
 	keyCtrlU     = 21
 	keyEnter     = '\r'
@@ -151,8 +152,12 @@ func bytesToKey(b []byte, pasteActive bool) (rune, []byte) {
 		switch b[0] {
 		case 1: // ^A
 			return keyHome, b[1:]
+		case 2: // ^B
+			return keyLeft, b[1:]
 		case 5: // ^E
 			return keyEnd, b[1:]
+		case 6: // ^F
+			return keyRight, b[1:]
 		case 8: // ^H
 			return keyBackspace, b[1:]
 		case 11: // ^K
@@ -738,6 +743,9 @@ func (t *Terminal) readLine() (line string, err error) {
 						return "", io.EOF
 					}
 				}
+				if key == keyCtrlC {
+					return "", io.EOF
+				}
 				if key == keyPasteStart {
 					t.pasteActive = true
 					if len(t.line) == 0 {