Update build-setup.sh

to fix `/home/USERNAME/1489223915/build.sh: line 27: syntax error near unexpected token (` while running build-setup.sh
diff --git a/build-setup.sh b/build-setup.sh
index fecf0dc..8d40a61 100755
--- a/build-setup.sh
+++ b/build-setup.sh
@@ -319,7 +319,7 @@
 EOF_GIT
 
   chmod a+x ${WORKSPACE}/bin/git-proxy
-  export PATH=${WORKSPACE}/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:${PATH}
+  export PATH="${WORKSPACE}/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:${PATH}"
 
   lock=${HOME}/build-setup.lock
   flock \${lock} git config --global core.gitProxy ${WORKSPACE}/bin/git-proxy