Portability fixes:

- Initialize outbuf with the expected size! fixes a segfault with musl.
- Really use __builtin_va_arg_pack_len().

--- src/makeguids.c 2014-12-28 10:30:36.731270900 +0100
+++ src/makeguids.c 2014-12-28 10:26:24.743259656 +0100
@@ -100,7 +100,7 @@ main(int argc, char *argv[])
                err(1, "makeguids: could not read \"%s\"", argv[1]);
 
        /* strictly speaking, this *has* to be too large. */
-       struct guidname *outbuf = calloc(inlen, sizeof (char));
+       struct guidname *outbuf = calloc(inlen, sizeof (struct guidname));
        if (!outbuf)
                err(1, "makeguids");

--- src/efivar.h    2014-12-28 10:30:36.731270900 +0100
+++ src/efivar.h    2014-12-28 10:26:57.359261112 +0100
@@ -85,7 +85,7 @@ efi_set_variable(efi_guid_t guid, const
                return -1;
        }
 
-       if (__va_arg_pack_len() == 0)
+       if (__builtin_va_arg_pack_len() == 0)
                return _efi_set_variable(guid, name, data, data_size,
                                         attributes, 0644);