vendor: update buildkit to v0.19.0-rc1

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

vendor/google.golang.org/grpc/internal/syscall/syscall_nonlinux.go

@@ -58,20 +58,20 @@ func GetRusage() *Rusage {
 
 // CPUTimeDiff returns the differences of user CPU time and system CPU time used
 // between two Rusage structs. It a no-op function for non-linux environments.
-func CPUTimeDiff(first *Rusage, latest *Rusage) (float64, float64) {
+func CPUTimeDiff(*Rusage, *Rusage) (float64, float64) {
 	log()
 	return 0, 0
 }
 
 // SetTCPUserTimeout is a no-op function under non-linux environments.
-func SetTCPUserTimeout(conn net.Conn, timeout time.Duration) error {
+func SetTCPUserTimeout(net.Conn, time.Duration) error {
 	log()
 	return nil
 }
 
 // GetTCPUserTimeout is a no-op function under non-linux environments.
 // A negative return value indicates the operation is not supported
-func GetTCPUserTimeout(conn net.Conn) (int, error) {
+func GetTCPUserTimeout(net.Conn) (int, error) {
 	log()
 	return -1, nil
 }