zproject_travis.gsl : do not shadow-compile with gcc-5 in "xenial" where it is default

Author: jimklimov

zproject_travis.gsl

@@ -412,22 +412,24 @@ matrix:
         - g++-4.9
         - gcc-4.9
 .   endif
+.if !defined(project.travis_dist) | (project.travis_dist ?<> "xenial")
   - env: BUILD_TYPE=default-Werror MATRIX_EVAL="CC=gcc-5 && CXX=g++-5"
     os: linux
-.if (project.travis_dist ?<> "")
+.   if (project.travis_dist ?<> "")
     dist: $(project.travis_dist)
-.endif
+.   endif
     addons:
       apt:
         sources:
         - ubuntu-toolchain-r-test
-.if (pkg_src_zeromq_dist ?<> "")
+.   if (pkg_src_zeromq_dist ?<> "")
         - *$(pkg_src_zeromq_dist)
-.endif
+.   endif
         packages:
         - *pkg_deps_common
         - g++-5
         - gcc-5
+.endif
   - env: BUILD_TYPE=default-Werror MATRIX_EVAL="CC=gcc-6 && CXX=g++-6"
     os: linux
 .if (project.travis_dist ?<> "")
@@ -505,7 +507,9 @@ matrix:
 .       if !(use_cxx_gcc_4_9 ?= 1)
   - env: BUILD_TYPE=default-Werror MATRIX_EVAL="CC=gcc-4.9 && CXX=g++-4.9"
 .       endif
+.       if !defined(project.travis_dist) | (project.travis_dist ?<> "xenial")
   - env: BUILD_TYPE=default-Werror MATRIX_EVAL="CC=gcc-5 && CXX=g++-5"
+.       endif
   - env: BUILD_TYPE=default-Werror MATRIX_EVAL="CC=gcc-6 && CXX=g++-6"
   - env: BUILD_TYPE=default-Werror MATRIX_EVAL="CC=gcc-7 && CXX=g++-7"
 .   endif