Updated Working on GNU Linux (markdown)

Working-on-GNU-Linux.md

@@ -56,7 +56,7 @@ Building with cmake on Linux is easy, just use the following:
 git clone https://github.com/raysan5/raylib.git raylib
 cd raylib
 mkdir build && cd build
-cmake -DSHARED=ON -DSTATIC=ON ..
+cmake -DBUILD_SHARED_LIBS=ON ..
 make
 make install
 ```