Build Failure on Ubuntu Xenial

[Anticept]

Autobuilding gmad using Travis CI, which defaults to Unbuntu Xenial for the build environment.

It is failing as follows:

The command "cd linux/gmake && make -j4" exited with 0.

0.02s$ cd ../../../../gmad && premake4 --bootil_lib="../bootil/lib/linux/gmake/" --bootil_inc="../bootil/include" gmake

Building configurations...

Running action 'gmake'...

Generating Makefile...

Generating GMad.make...

Done.

The command "cd ../../../../gmad && premake4 --bootil_lib="../bootil/lib/linux/gmake/" --bootil_inc="../bootil/include" gmake" exited with 0.

1.30s$ make -j4

==== Building GMad (release) ====

gmadd.cpp

extract_gmad.cpp

create_gmad.cpp

Creating obj/Release

src/create_gmad.cpp: In function ‘bool CreateAddon::Create(Bootil::Buffer&, Bootil::BString, Bootil::String::List&, Bootil::BString, Bootil::BString)’:

src/create_gmad.cpp:92:124: error: ‘errno’ was not declared in this scope

     Output::Warning( "File '%s' seems to be empty, or we couldn't get its size! (errno=%i)\n", ( strFolder + *f ).c_str(), errno );

                                                                                                                            ^

GMad.make:109: recipe for target 'obj/Release/create_gmad.o' failed

make[1]: *** [obj/Release/create_gmad.o] Error 1

make[1]: *** Waiting for unfinished jobs....

Makefile:16: recipe for target 'GMad' failed

make: *** [GMad] Error 2

The command "make -j4" exited with 2.

[Anticept]

Changed .travis.yml file to use dist: bionic and the problem is resolved.