x11-fonts/ots: unbreak build after 4aec6e12

In file included from ../tests/cff_charstring_test.cc:7:
In file included from /usr/local/include/gtest/gtest.h:64:
In file included from /usr/local/include/gtest/gtest-assertion-result.h:46:
In file included from /usr/local/include/gtest/gtest-message.h:57:
/usr/local/include/gtest/internal/gtest-port.h:270:2: error: C++ versions less than C++14 are not supported.
 #error C++ versions less than C++14 are not supported.
  ^

Reported by:	pkg-fallout