journal: use FSS_HEADER_SIGNATURE at one more place

src/journal/journalctl-authenticate.c

@@ -139,7 +139,7 @@ int action_setup_keys(void) {
                                r, "Failed to set file attributes on a temporary file for '%s', ignoring: %m", path);
 
         struct FSSHeader h = {
-                .signature = { 'K', 'S', 'H', 'H', 'R', 'H', 'L', 'P' },
+                .signature = FSS_HEADER_SIGNATURE,
                 .machine_id = machine,
                 .boot_id = boot,
                 .header_size = htole64(sizeof(h)),

src/libsystemd/sd-journal/journal-authenticate.c

@@ -392,7 +392,7 @@ int journal_file_fss_load(JournalFile *f) {
         if (header == MAP_FAILED)
                 return -errno;
 
-        if (memcmp(header->signature, FSS_HEADER_SIGNATURE, 8) != 0)
+        if (memcmp(header->signature, (const uint8_t[]) FSS_HEADER_SIGNATURE, 8) != 0)
                 return -EBADMSG;
 
         if (header->incompatible_flags != 0)

src/libsystemd/sd-journal/journal-def.h

@@ -261,7 +261,7 @@ assert_cc(sizeof(struct Header) == sizeof(struct Header__packed));
 assert_cc(sizeof(struct Header) == 272);
 
 #define FSS_HEADER_SIGNATURE                                            \
-        ((const char[]) { 'K', 'S', 'H', 'H', 'R', 'H', 'L', 'P' })
+        { 'K', 'S', 'H', 'H', 'R', 'H', 'L', 'P' }
 
 struct FSSHeader {
         uint8_t signature[8]; /* "KSHHRHLP" */