Since we can sign i386 PE/COFF images, run the tests on both x86-64 and
i386 binaries.
We do this by moving test.pecoff to test-<arch>.pecoff, and using
automake's parallel-test option to add a wrapper to each test execution.
This wrapper calls each test once per arch (as defined in TEST_ARCHES),
and checks for failures in any invocation.
Signed-off-by: Jeremy Kerr <jeremy.kerr@canonical.com>
