First, on x86-64 Linux does not reserve lower 2 Gb of the address space,
and a space saving trick in the runtime did not work properly, confusing
pointers and failure generation numbers together.
Second, we ignored protocol conformances inside the executable (only
considered shared libraries).
Swift SVN r25972
Most tests were using %swift or similar substitutions, which did not
include the target triple and SDK. The driver was defaulting to the
host OS. Thus, we could not run the tests when the standard library was
not built for OS X.
Swift SVN r24504
