CI: add Arm support to travis CI matrix (#6436)

Summary:
This patch based on https://github.com/facebook/rocksdb/issues/5932 offers a better solution to add arm64 to TravisCI matrix.
Really thank adamretter for initiating Arm CI setup.

Difference comparing to amd64:
1. For CMake, as no official arm64 release ready on Kitware page,
a third party (conda-forge) released one is used instead of
building from source. The main reason is to save CI time.
2. Explicit export JAVA_HOME on arm64
3. Disable mingw test

Signed-off-by: Yuqi Gu <yuqi.gu@arm.com>
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6436

Differential Revision: D20428505

Pulled By: pdillinger

fbshipit-source-id: 81ef02435e41480bb71710b783d85ebf452ce926

.travis.yml

@@ -5,6 +5,7 @@ os:
   - osx
 arch:
   - amd64
+  - arm64
   - ppc64le
 compiler:
   - clang
@@ -69,6 +70,9 @@ matrix:
     arch: ppc64le
   - os: osx
     compiler: gcc
+  - os : linux
+    arch: arm64
+    env: JOB_NAME=cmake-mingw
   - os: linux
     arch: ppc64le
     env: JOB_NAME=cmake-mingw
@@ -89,6 +93,10 @@ install:
   - if [[ "${JOB_NAME}" == cmake* ]] && [ "${TRAVIS_OS_NAME}" == linux ]; then
       CMAKE_DIST_URL="https://github.com/pdillinger/rocksdb/releases/download/cmake-3.14.5/cmake-3.14.5-Linux-$(uname -m).tar.bz2";
       TAR_OPT="--strip-components=1 -xj";
+      if [ "aarch64" == "$(uname -m)" ]; then
+        sudo apt-get install -y libuv1 librhash0;
+        sudo apt-get upgrade -y libstdc++6;
+      fi;
       mkdir cmake-dist && curl --silent --fail --show-error --location "${CMAKE_DIST_URL}" | tar -C cmake-dist ${TAR_OPT} && export PATH=$PWD/cmake-dist/bin:$PATH;
     fi
   - |