'array' test name conflict with #include <array>

When compiling the testsuite with -DEIGEN_SPLIT_LARGE_TESTS=OFF, the parallel make sometime hits to include the ./test/array binary by error, since array is also a C++ header included in code.

#include <array>

In file included from /usr/include/c++/7.5.0/tuple:39:0,
                 from /usr/include/c++/7.5.0/functional:54,
                 from /.../.../eigen/Eigen/Core:285,
                 from /.../.../eigen/Eigen/QR:11,
                 from /.../.../eigen/test/main.h:310,
                 from /.../.../eigen/test/ref.cpp:17:

.../eigen/build/test/array:33865:197: error: stray ‘\10’ in program
 ��   k  �B     �  �T   Ks ��  
                               �  �& �  �
                                                                       ^
.../eigen/build/test/array:33924:91: error: stray ‘\34’ in program
 ?[   
      �  
                                                                                           ^
.../eigen/build/test/array:33865:201: error: stray ‘\377’ in program
 �  0B   
         s  @@0&   [� 1�     
                             : 4
te~   �s  u  �H  �  �s   ^   �  ;  ��   k  �B     �  �T   Ks ��  
                                                                 �  �& �  �