Build with gradle 4.2

Reviewed at https://reviews.apache.org/r/62524/
diff --git a/builder/deb/debian-jessie/Dockerfile b/builder/deb/debian-jessie/Dockerfile
index 077d2b6..1983fb6 100644
--- a/builder/deb/debian-jessie/Dockerfile
+++ b/builder/deb/debian-jessie/Dockerfile
@@ -51,9 +51,9 @@
 RUN git clone --depth 1 https://github.com/benley/gradle-packaging \
   && cd gradle-packaging \
   && apt-get -y install ruby ruby-dev unzip wget \
-  && gem install fpm && ./gradle-mkdeb.sh 3.1 \
+  && gem install fpm && ./gradle-mkdeb.sh 4.2 \
   && apt-get -y install gdebi-core \
-  && gdebi --non-interactive gradle-3.1_3.1-2_all.deb \
+  && gdebi --non-interactive gradle-4.2_4.2-2_all.deb \
   && cd .. && rm -rf gradle-packaging
 
 ADD build.sh /build.sh
diff --git a/builder/deb/ubuntu-trusty/Dockerfile b/builder/deb/ubuntu-trusty/Dockerfile
index 595196a..99c5481 100644
--- a/builder/deb/ubuntu-trusty/Dockerfile
+++ b/builder/deb/ubuntu-trusty/Dockerfile
@@ -47,9 +47,9 @@
 RUN git clone --depth 1 https://github.com/benley/gradle-packaging \
   && cd gradle-packaging \
   && apt-get -y install ruby ruby-dev unzip wget \
-  && gem install fpm && ./gradle-mkdeb.sh 3.1 \
+  && gem install fpm && ./gradle-mkdeb.sh 4.2 \
   && apt-get -y install gdebi-core \
-  && gdebi --non-interactive gradle-3.1_3.1-2_all.deb \
+  && gdebi --non-interactive gradle-4.2_4.2-2_all.deb \
   && cd .. && rm -rf gradle-packaging
 
 ADD build.sh /build.sh
diff --git a/builder/deb/ubuntu-xenial/Dockerfile b/builder/deb/ubuntu-xenial/Dockerfile
index a32f4bc..dfdce15 100644
--- a/builder/deb/ubuntu-xenial/Dockerfile
+++ b/builder/deb/ubuntu-xenial/Dockerfile
@@ -47,9 +47,9 @@
 RUN git clone --depth 1 https://github.com/benley/gradle-packaging \
   && cd gradle-packaging \
   && apt-get -y install ruby ruby-dev unzip wget \
-  && gem install fpm && ./gradle-mkdeb.sh 3.1 \
+  && gem install fpm && ./gradle-mkdeb.sh 4.2 \
   && apt-get -y install gdebi-core \
-  && gdebi --non-interactive gradle-3.1_3.1-2_all.deb \
+  && gdebi --non-interactive gradle-4.2_4.2-2_all.deb \
   && cd .. && rm -rf gradle-packaging
 
 ADD build.sh /build.sh
diff --git a/specs/debian/control b/specs/debian/control
index 9625ecf..df86306 100644
--- a/specs/debian/control
+++ b/specs/debian/control
@@ -3,7 +3,7 @@
 Maintainer: The Apache Aurora authors <dev@aurora.apache.org>
 Build-Depends: debhelper (>= 9),
  java8-sdk | openjdk-8-jdk,
- gradle (>= 3.1) | gradle-3.1,
+ gradle (>= 4.2) | gradle-4.2,
  python-all-dev,
  libkrb5-dev,
  curl,
diff --git a/specs/rpm/aurora.spec b/specs/rpm/aurora.spec
index 2b3c9fe..e1eff9c 100644
--- a/specs/rpm/aurora.spec
+++ b/specs/rpm/aurora.spec
@@ -34,7 +34,7 @@
 %endif
 
 %if %{?!GRADLE_VERSION:1}0
-%global GRADLE_VERSION 3.1
+%global GRADLE_VERSION 4.2
 %endif
 
 %if %{?!JAVA_VERSION:!}0