games/xminehunter: Fix build with Clang 6

./bitmaps/bomb:5:28: error: constant expression evaluates to 144 which cannot be narrowed to type 'char' [-Wc++11-narrowing]

0x00, 0x00, 0x00, 0x00, 0x90, 0x00, 0x00, 0x00, 0x40, 0x02, 0x00, 0x00,
                        ^~~~

http://beefy12.nyi.freebsd.org/data/head-amd64-default/p475478_s336801/logs/errors/xminehunter-0.4_4.log

• Actually install the binary as executable (broken 5 years ago in r337083)