games/searchandrescue: Fix build on 12.0-CURRENT

Respect CPPFLAGS and stop doing weird things like defining __cplusplus
in the build itself.

In file included from <built-in>:388:
<command line>:8:9: warning: 'cplusplus' macro redefined [-Wmacro-redefined]
#define cplusplus 1

^

<built-in>:384:9: note: previous definition is here
#define __cplusplus 201402L

^

In file included from disk.cpp:1:
In file included from /usr/include/c++/v1/stdio.h:102:
/usr/include/c++/v1/__config:327:20: error: cannot combine with previous 'char16_t' declaration specifier
typedef __char16_t char16_t;

^

/usr/include/c++/v1/__config:328:20: error: cannot combine with previous 'char32_t' declaration specifier
typedef __char32_t char32_t;

^

http://beefy12.nyi.freebsd.org/data/head-amd64-default/p475478_s336801/logs/errors/SearchAndRescue-1.4.0_6.log

While here

• Add license
• Add missing dependencies