Install ninja dep

Ninja is a prerequisite for the build. On Ubuntu install it with apt-get,
and on GitHub's macOS Docker image it needs to come from Homebrew.

Author: ptomato

.github/workflows/android.yml

@@ -39,7 +39,7 @@ jobs:
           sudo ln -fs /usr/share/zoneinfo/UTC /etc/localtime
           sudo apt-get update
           sudo apt-get upgrade -y
-          sudo apt-get install -y apt-utils sudo lsb-core git python nodejs npm wget openjdk-8-jre openjdk-8-jdk
+          sudo apt-get install -y apt-utils sudo lsb-core git python ninja-build nodejs npm wget openjdk-8-jre openjdk-8-jdk
 
       - name: Export settings from npm package
         run: npm run export_npm_env

.github/workflows/ios.yml

@@ -19,6 +19,7 @@ jobs:
     - name: Setup V8 build environment
       run: |
         brew install coreutils
+        brew install ninja
         scripts/setup.sh -r ${V8_VERSION} ios
 
     - name: Patch V8