LibreSSL disables the CMS subsystem, so sign-file.c needs to fall back to using
PKCS#7 in that case.

Signed-off-by: Felix Fietkau <nbd@nbd.name>

--- a/scripts/sign-file.c
+++ b/scripts/sign-file.c
@@ -39,7 +39,7 @@
  * signing with anything other than SHA1 - so we're stuck with that if such is
  * the case.
  */
-#if OPENSSL_VERSION_NUMBER < 0x10000000L
+#if defined(LIBRESSL_VERSION_NUMBER) || OPENSSL_VERSION_NUMBER < 0x10000000L
 #define USE_PKCS7
 #endif
 #ifndef USE_PKCS7