Avoid using C99 declaration-after-statement syntax

Add a dedicated `{}` block to contain a local variable instead.
diff --git a/libarchive/archive_write_set_format_iso9660.c b/libarchive/archive_write_set_format_iso9660.c
index 4e91097..c0ca435 100644
--- a/libarchive/archive_write_set_format_iso9660.c
+++ b/libarchive/archive_write_set_format_iso9660.c
@@ -4074,8 +4074,10 @@
 	memset(info.s, 0, info_size);
 	opt = 0;
 #if defined(HAVE__CTIME64_S)
-	__time64_t iso9660_birth_time_tmp = (__time64_t) iso9660->birth_time; //time_t may be shorter than 64 bits
-	_ctime64_s(buf, sizeof(buf), &(iso9660_birth_time_tmp));
+	{
+		__time64_t iso9660_birth_time_tmp = (__time64_t) iso9660->birth_time; //time_t may be shorter than 64 bits
+		_ctime64_s(buf, sizeof(buf), &(iso9660_birth_time_tmp));
+	}
 #elif defined(HAVE_CTIME_R)
 	ctime_r(&(iso9660->birth_time), buf);
 #else
diff --git a/libarchive/test/test_fuzz.c b/libarchive/test/test_fuzz.c
index 71bf3ff..ce7b866 100644
--- a/libarchive/test/test_fuzz.c
+++ b/libarchive/test/test_fuzz.c
@@ -110,8 +110,9 @@
 		} else {
 			for (i = 0; filesets[n].names[i] != NULL; ++i)
 			{
+				char *newraw;
 				tmp = slurpfile(&size, filesets[n].names[i]);
-				char *newraw = realloc(rawimage, oldsize + size);
+				newraw = realloc(rawimage, oldsize + size);
 				if (!assert(newraw != NULL))
 				{
 					free(rawimage);