NIFs: fix "warning: initializer-string for character array is too long"

array size is 64 but initializer has size 65 (including the null
terminating character).

Keep it 64 by using the array syntax, instead of "".

Signed-off-by: Davide Bettio <davide@uninstall.it>

Author: bettio

src/libAtomVM/nifs.c

@@ -4163,7 +4163,13 @@ static term nif_console_print(Context *ctx, int argc, term argv[])
     return OK_ATOM;
 }
 
-static char b64_table[64] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+static char b64_table[64] = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
+                             'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
+                             'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd',
+                             'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
+                             'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x',
+                             'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7',
+                             '8', '9', '+', '/'};
 
 // per https://tools.ietf.org/rfc/rfc4648.txt