tools: Write msvc-compatible frozen content.

The msvc compiler doesn't accept zero-sized arrays so let the freezing
process generate compatible C code in case no modules are found and the
involved arrays are all empty.  This doesn't affect the functionality in
any way because those arrays only get accessed when mp_frozen_mpy_names
contains names, i.e.  when modules are actually found.

tools/make-frozen.py

@@ -50,7 +50,7 @@ print("const uint32_t mp_frozen_str_sizes[] = {")
 for f, st in modules:
     print("%d," % st.st_size)
 
-print("};")
+print("0};")
 
 print("const char mp_frozen_str_content[] = {")
 for f, st in modules:
@@ -82,4 +82,4 @@ for f, st in modules:
     chrs.append('\\0"')
     print("".join(chrs))
 
-print("};")
+print('"\\0"};')

tools/makemanifest.py

@@ -327,7 +327,7 @@ def main():
             b"    (qstr_pool_t*)&mp_qstr_const_pool, MP_QSTRnumber_of, 0, 0\n"
             b"};\n"
             b'const char mp_frozen_mpy_names[1] = {"\\0"};\n'
-            b"const mp_raw_code_t *const mp_frozen_mpy_content[0] = {};\n"
+            b"const mp_raw_code_t *const mp_frozen_mpy_content[1] = {NULL};\n"
         )
 
     # Generate output