travis: bump the Secure Transport build to use xcode 10

Due to an issue with travis
(https://github.com/travis-ci/travis-ci/issues/9956) we've been using
Xcode 9.2 for darwinssl builds for a while. Now xcode 10 is offered as
an alternative and as it builds curl+darwinssl fine that seems like a
better choice.

Closes #3062

diff --git a/.travis.yml b/.travis.yml
index cf39d26b5e7089e89acf982592de24e8f9eeaaf3..1610d3e8b1e8829975e1f1d05b55f19c37335ad8 100644 (file)
--- a/.travis.yml
+++ b/.travis.yml
@@ -107,7 +107,7 @@ matrix:
           env: T=debug C="--with-ssl=/usr/local/opt/libressl --with-libmetalink"
         - os: osx
           compiler: clang
-          osx_image: xcode9.2
+          osx_image: xcode10
           env: T=debug C="--without-ssl --with-darwinssl --with-libmetalink"
         - os: osx
           compiler: clang