package/ucl: fix build with host gcc 6.x
ucl fails with the following error when using gcc 6.x on the host:
checking whether your compiler passes the ACC conformance test... FAILED
configure:
configure: Your compiler failed the ACC conformance test - for details see
configure: `config.log'. Please check that log file and consider sending
configure: a patch or bug-report to <markus@oberhumer.com>.
configure: Thanks for your support.
configure:
configure: error: ACC conformance test failed. Stop.
Fix the issue by using the ISO C90 standard.
Signed-off-by: Martin Bark <martin@barkynet.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>