Use the before_install tag to set the permission of the dep script.

Change-Id: I2eba65e1af47ce3affb7f6bd8d74ab1ddbccb06f

Author: irbull

.travis.yml

@@ -1,6 +1,6 @@
 os: osx
 language: cpe
 compiler: clang
-before_script:
- - chmod build-node.sh
-install: ./build-node.sh
+before_install:
+ - chmod -x build-node.sh
+install: sh ./build-node.sh

build-node.sh

@@ -1,4 +1,5 @@
-git checkout git@github.com:nodejs/node.git
+git clone https://github.com/nodejs/node.git
 cd node
+git checkout v5.9.1
 ./configure
 make