crypto/x509: fix build break on darwin/{arm,arm64}

Fix build error on darwin/{arm,arm64} caused by a62ae9f6.

Change-Id: I7da4d147a529b11b3e71352a9276a57595ec4b05
Reviewed-on: https://go-review.googlesource.com/21356
Run-TryBot: Dave Cheney <dave@cheney.net>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/crypto/x509/root_darwin_arm_gen.go

@@ -187,6 +187,6 @@ package x509
 func loadSystemRoots() (*CertPool, error) {
 	p := NewCertPool()
 	p.AppendCertsFromPEM([]byte(systemRootsPEM))
-	return p
+	return p, nil
 }
 `

src/crypto/x509/root_darwin_armx.go

@@ -13,7 +13,7 @@ package x509
 func loadSystemRoots() (*CertPool, error) {
 	p := NewCertPool()
 	p.AppendCertsFromPEM([]byte(systemRootsPEM))
-	return p
+	return p, nil
 }
 
 const systemRootsPEM = `