build: fix warnings from GCC 15

Signed-off-by: He Xian <hexian000@outlook.com>

Author: hexian000

contrib/csnippets/codec/base64.c

@@ -6,7 +6,7 @@
 #include <stddef.h>
 #include <stdint.h>
 
-static const unsigned char encoding_table[64] =
+static const unsigned char encoding_table[] =
 	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 
 bool base64_encode(

src/ruleset/marshal.c

@@ -132,8 +132,8 @@ static void
 marshal_number(lua_State *restrict L, struct vbuffer *restrict *restrict pvbuf)
 {
 	const int idx = 1;
-	static const char prefix[3] = "-0x";
-	static const char xdigits[16] = "0123456789abcdef";
+	static const char prefix[] = "-0x";
+	static const char xdigits[] = "0123456789abcdef";
 	unsigned char buf[120];
 
 	/* Handle integer values */