Disables explicit compiler definitions

Comments out the export of CC and CXX environment variables.
This allows the system to use default compilers or rely on other mechanisms to set them.

Author: zhigenzhao

setup_ubuntu.sh

@@ -1,5 +1,5 @@
-export CC=/usr/bin/gcc
-export CXX=/usr/bin/g++
+# export CC=/usr/bin/gcc
+# export CXX=/usr/bin/g++
 mkdir -p tmp
 cd tmp
 git clone https://github.com/XR-Robotics/XRoboToolkit-PC-Service.git