Nice work on the game! Seem nice from the screenshot! Although I have not yet managed to compile for linux.

It would be nice if you made a demo video.

One tip: separate both branches into 'master' and 'debug'. At least to separate in a branch what works and in another branch what you are modifying.

Building on Linux should be as easy as something like this :

git clone https://github.com/liballeg/allegro5.git Allegro52X
git clone https://github.com/EdgarReynaldo/EagleGUI.git Eagle
git clone https://github.com/EdgarReynaldo/Skyline2.git Skyline

sudo apt-get install liballegro5-dev libphysfs-dev

cd Allegro52X
mkdir build
cd build
cmake-gui ..
make -j 8 install

cd ../../Eagle
mkdir build
cd build
cmake-gui ..
make -j 8 install

sudo ldconfig

cd ../../Skyline
mkdir build
cd build
cmake-gui ..
make -j 8 install

(I am testing it now on Ubuntu 18.04)

rmbeer2$: I'm fixing the bugs now.

UPDATE
All the bugs are fixed now. Eagle and Skyline should build easily on Linux now.

Works on Mac! But I had to mangle your CMake files (I always struggle with CMake, it's horrible)
{"name":"612579","src":"\/\/djungxnpq2nug.cloudfront.net\/image\/cache\/7\/4\/74eeeed58361e74347160268d4432a4b.jpg","w":628,"h":480,"tn":"\/\/djungxnpq2nug.cloudfront.net\/image\/cache\/7\/4\/74eeeed58361e74347160268d4432a4b"}

i can run SkyLine! \o/
It is a good game, although I have a problem with the size of the window, it is too big for my screen. Also the explosions collide with any bullet, which even collides with mine, trying to explode the enemy bullets there comes a time when my own explosions explode the city more and more to the center, and I have to wait for it to dissipate before firing again. .
It is difficult to try to shoot at the precise moment and time. :S Although this is good, it is the difficulty of the game.

Whether you win or lose is determined by the damage the city takes? Because I have destroyed my own city and I have won the same anyway.

EDIT:
Lasers are a cheat! I can sweep the area by creating a wall and easily blowing up all the missiles, although the speed of the machine drops drastically.