Always print output on failure in cmake tests on Travis.

[iphydf]

Not only the second time it fails.

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This change is 

[robinlinden]

Reviewed 1 of 1 files at r1.
Reviewable status: 0 of 1 approvals obtained

[codecov]

Codecov Report

Merging #1107 into master will increase coverage by 1%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #1107    +/-   ##
=======================================
+ Coverage    81.3%   82.4%    +1%     
=======================================
  Files          79      80     +1     
  Lines       14219   14316    +97     
=======================================
+ Hits        11572   11804   +232     
+ Misses       2647    2512   -135

Impacted Files	Coverage Δ
toxav/toxav.c	68% <0%> (-1.7%)	⬇️
toxcore/group.c	71.7% <0%> (-1.5%)	⬇️
toxav/msi.c	65.3% <0%> (-1.4%)	⬇️
auto_tests/tox_many_tcp_test.c	100% <0%> (ø)
auto_tests/toxav_many_test.c	97.2% <0%> (+0.6%)	⬆️
toxcore/Messenger.c	85.8% <0%> (+0.8%)	⬆️
toxcore/network.c	83.4% <0%> (+1.4%)	⬆️
toxcore/onion_client.c	95% <0%> (+1.7%)	⬆️
toxcore/TCP_connection.c	78.2% <0%> (+2.8%)	⬆️
toxcore/onion.c	98.7% <0%> (+3.2%)	⬆️
... and 5 more

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