autotools: Fix autoconf-archive compatibility issues

autoconf-archive 2019-01-06 changed the setup of code coverage support.
Deal with both old and new. Based on Patrick Venture's similar patch in
other repositories[1].

[1] https://github.com/openbmc/phosphor-pid-control/commit/90e9dbcae6c1df3127dd3de41f9d1e1b5a438828

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: Ibf7b240f0b3e78ba80f587de7a0f8a1e804a7446
2 files changed