buildserver: setup env vars using standard script

bash provides a standard file location for a script to be run when the
shell starts: /etc/profile.d/  This converts the scattered bits of code for
making ~/.bsenv into a single provisioning script to generate
/etc/profile.d/bsenv.sh, which gets automatically executed when bash starts

buildserver/setup-env-vars

@@ -0,0 +1,16 @@
+#!/bin/sh
+#
+# sets up the environment vars needed by the build process
+
+set -e
+set -x
+
+bsenv=/etc/profile.d/bsenv.sh
+
+echo "# generated on "`date` > $bsenv
+
+echo export ANDROID_HOME=$1 >> $bsenv
+echo export ANDROID_NDK_HOME=$2 >> $bsenv
+echo 'export PATH=$PATH:${ANDROID_HOME}/tools:${ANDROID_HOME}/platform-tools:/opt/gradle/bin' >> $bsenv
+
+chmod 0644 $bsenv