updating pip invocation to avoid pypa/pip#3826

Author: tfoote

doc/ardupilot/readme.md

@@ -124,8 +124,10 @@ git submodule update --init --recursive
 ~~~
 
 ### Install mavproxy
+
+You will need mavproxy installed from pip on your system.
 ~~~
-sudo pip install --target=/opt/sasc/lib/python/site-packages/ mavproxy --install-option="--install-scripts=/opt/sasc/bin"
+sudo pip install mavproxy
 ~~~
 
 # Run Simulation from binary installation

packaging/build_package.sh

@@ -39,15 +39,15 @@ git clone https://github.com/tfoote/ardupilot.git -b uctf-dev
 echo "Building Ardupilot..."
 cd ardupilot
 export PATH=${PATH}:${WS}/ardupilot/Tools/autotest
-./Tools/scripts/install-prereqs-ubuntu.sh
+# ./Tools/scripts/install-prereqs-ubuntu.sh
 git submodule update --init --recursive
 ./waf configure --prefix=${INSTALL}
 ./waf
 ./waf install
 
 
 echo "Installing mavproxy"
-pip install mavproxy --target=${INSTALL}/lib/python/site-packages/ --install-option="--install-scripts=/opt/sasc/bin"
+pip install mavproxy --system --target=${INSTALL}/lib/python/site-packages/ --install-option="--install-scripts=/opt/sasc/bin"
 
 
 echo "generating control file"