layout: fix build on i386
Due to the (lack of) precision of floating-point values, comparison
results may differ slightly between architectures, leading to the
check_stretching
test failing when building for i386. This can be
fixed by adjusting the value against which we compare the ratio between
x/y scaling factors in calculate_transformation
.
Changing the test condition instead would go against the point of setting a (soft) limit to 5%.
With this patch, squeekboard builds successfully on arm64, i386 and amd64.