ci: bump version of Oniguruma to 6.9.1

Update deb to get fix https://bugs.launchpad.net/ubuntu/+source/dpkg/+bug/1730627

Signed-off-by: Alexander Bezzubov <[email protected]>

.travis.yml

@@ -1,3 +1,4 @@
+dist: trusty
 language: go
 go:
   - '1.11.x'
@@ -7,11 +8,14 @@ env:
   global:
     - LD_LIBRARY_PATH="/usr/local/lib":${LD_LIBRARY_PATH}
     - GO111MODULE=on
-
 addons:
   apt:
     packages:
       - libonig-dev
 
+before_install:
+  - wget http://archive.ubuntu.com/ubuntu/pool/universe/libo/libonig/libonig-dev_6.9.1-1_amd64.deb
+  - sudo apt-get install -y dpkg  # dpkg >= 1.17.5ubuntu5.8, which fixes https://bugs.launchpad.net/ubuntu/+source/dpkg/+bug/1730627- sudo dpkg -i libonig-dev_6.9.1-1_amd64.deb
+  - sudo dpkg -i libonig-dev_6.9.1-1_amd64.deb
 script:
   - go test -v --cover -race