How to deal with test data in ouf of source tree builds?

[Paul Menzel]

Dear Autoconf folks,


When doing an out of source build of Unbound, the test suite fails with 
the error below.

```
test signature verify functions
testpkts error: could not open file testdata/test_signatures.1: No such 
file or directory
Makefile:304: recipe for target 'test' failed
make: *** [test] Error 1
```

In the source directory there is a directory `testdata`, and that gets 
referenced incorrectly in `testcode/unitverify.c`.

```
void
verify_test(void)
{
        unit_show_feature("signature verify");
#ifdef USE_SHA1
        verifytest_file("testdata/test_signatures.1", "20070818005004");
#endif
#if defined(USE_DSA) && defined(USE_SHA1)
        verifytest_file("testdata/test_signatures.2", "20080414005004");
        verifytest_file("testdata/test_signatures.3", "20080416005004");
[…]
```

Unfortunately, I couldn’t find any documentation how to deal with test 
data when building out of the source tree. Should the test data be 
copied to the build directory, despite it being not changed, should it 
be linked, or does the code need to reference only absolute paths, and 
therefore has to be preprocessed(?)?


Kind regards,

Paul