According to commit ea568419
the stack normally grows downwards, except on HP PA-RISC where
it grows upwards. Because determining the stack direction is not
possible in a portable way, let us determine the default STACK_DIRECTION
in CMake based on the ISA.

On clang 16.0.6 running on and targeting AMD64, STACK_DIRECTION=1 is
being incorrectly detected, causing the failure of a number of tests.