travis: switch to Bionic

To judge from fc412fe4cee960, back in 2016 it was the latest version
of Ubuntu available on Travis CI. Now build tools there are too old
for testing purposes.

Other than that, Ubuntu Trusty hasn't been supported at https://apt.llvm.org/
since August 2019, which makes it kind of hard at this point to bring the latest clang
along with ASan, UBsan, Msan and libFuzzer to Travis CI.

diff --git a/.travis.yml b/.travis.yml
index a4f51f3ed0e02b63ef84dbc40630b7e3a0ca00bb..85797e83083ca0e68ef803006f39d8196962923a 100644 (file)
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,7 +1,7 @@
 language: c
 
 sudo: required
-dist: trusty
+dist: bionic
 
 git:
   depth: 1500