Add pkg-config dependency

.travis.yml

@@ -18,6 +18,7 @@ addons:
   apt:
     packages:
       - clang
+      - pkg-config
 bundler_args: --jobs=4 --retry=3
 before_install:
   - if [ "$TRAVIS_OS_NAME" == "linux" ]; then gem update bundler; fi

README.md

@@ -84,6 +84,7 @@ Building the V8 library from source imposes the following requirements:
   [#217](https://github.com/cowboyd/libv8/issues/217) for state of other
   platforms.
 * Python 2
+* pkg-config
 
 ### Using a git version
 

release/x86-linux/Vagrantfile

@@ -78,7 +78,7 @@ Vagrant.configure(2) do |config|
     sudo apt-add-repository ppa:brightbox/ruby-ng
     sudo apt-get update
     sudo apt-get dist-upgrade -y
-    sudo apt-get install -y build-essential git ruby-switch ruby2.3 ruby2.3-dev
+    sudo apt-get install -y build-essential git ruby-switch ruby2.3 ruby2.3-dev pkg-config
     sudo ruby-switch --set ruby2.3
     sudo gem install bundler
   SHELL

release/x86_64-linux/Vagrantfile

@@ -78,7 +78,7 @@ Vagrant.configure(2) do |config|
     sudo apt-add-repository ppa:brightbox/ruby-ng
     sudo apt-get update
     sudo apt-get dist-upgrade -y
-    sudo apt-get install -y build-essential git ruby-switch ruby2.3 ruby2.3-dev
+    sudo apt-get install -y build-essential git ruby-switch ruby2.3 ruby2.3-dev pkg-config
     sudo ruby-switch --set ruby2.3
     sudo gem install bundler
   SHELL