gawk: ptest fixes

gawk: ptest fixes

In minimal images all tests pass due to a missing dependency on make.
Add the missing dependecy.

The test list created by the run-ptest script is incorrect as it includes
entries like "fi". Simplify it and correct it.

Some tests are skipped due to mpfr not being enabled. Correctly mark these
as SKIP.

Some tests need the "../gawk" script, create a link to it so the tests
work correctly.

Also print more information in the failed test cases.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>