[SPARK-25335][BUILD] Skip Zinc downloading if it's installed in the system

## What changes were proposed in this pull request?

Zinc is 23.5MB (tgz).
```
$ curl -LO https://downloads.lightbend.com/zinc/0.3.15/zinc-0.3.15.tgz
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 23.5M  100 23.5M    0     0  35.4M      0 --:--:-- --:--:-- --:--:-- 35.3M
```

Currently, Spark downloads Zinc once. However, it occurs too many times in build systems. This PR aims to skip Zinc downloading when the system already has it.
```
$ build/mvn clean
exec: curl --progress-bar -L https://downloads.lightbend.com/zinc/0.3.15/zinc-0.3.15.tgz
######################################################################## 100.0%
```

This will reduce many resources(CPU/Networks/DISK) at least in Mac and Docker-based build system.

## How was this patch tested?

Pass the Jenkins.

Closes apache#22333 from dongjoon-hyun/SPARK-25335.

Authored-by: Dongjoon Hyun <[email protected]>
Signed-off-by: Sean Owen <[email protected]>

Author: dongjoon-hyun

build/mvn

@@ -67,6 +67,9 @@ install_app() {
   fi
 }
 
+# See simple version normalization: http://stackoverflow.com/questions/16989598/bash-comparing-version-numbers
+function version { echo "$@" | awk -F. '{ printf("%03d%03d%03d\n", $1,$2,$3); }'; }
+
 # Determine the Maven version from the root pom.xml file and
 # install maven under the build/ folder if needed.
 install_mvn() {
@@ -75,8 +78,6 @@ install_mvn() {
   if [ "$MVN_BIN" ]; then
     local MVN_DETECTED_VERSION="$(mvn --version | head -n1 | awk '{print $3}')"
   fi
-  # See simple version normalization: http://stackoverflow.com/questions/16989598/bash-comparing-version-numbers
-  function version { echo "$@" | awk -F. '{ printf("%03d%03d%03d\n", $1,$2,$3); }'; }
   if [ $(version $MVN_DETECTED_VERSION) -lt $(version $MVN_VERSION) ]; then
     local APACHE_MIRROR=${APACHE_MIRROR:-'https://www.apache.org/dyn/closer.lua?action=download&filename='}
 
@@ -91,15 +92,23 @@ install_mvn() {
 
 # Install zinc under the build/ folder
 install_zinc() {
-  local zinc_path="zinc-0.3.15/bin/zinc"
-  [ ! -f "${_DIR}/${zinc_path}" ] && ZINC_INSTALL_FLAG=1
-  local TYPESAFE_MIRROR=${TYPESAFE_MIRROR:-https://downloads.lightbend.com}
+  local ZINC_VERSION=0.3.15
+  ZINC_BIN="$(command -v zinc)"
+  if [ "$ZINC_BIN" ]; then
+    local ZINC_DETECTED_VERSION="$(zinc -version | head -n1 | awk '{print $5}')"
+  fi
 
-  install_app \
-    "${TYPESAFE_MIRROR}/zinc/0.3.15" \
-    "zinc-0.3.15.tgz" \
-    "${zinc_path}"
-  ZINC_BIN="${_DIR}/${zinc_path}"
+  if [ $(version $ZINC_DETECTED_VERSION) -lt $(version $ZINC_VERSION) ]; then
+    local zinc_path="zinc-${ZINC_VERSION}/bin/zinc"
+    [ ! -f "${_DIR}/${zinc_path}" ] && ZINC_INSTALL_FLAG=1
+    local TYPESAFE_MIRROR=${TYPESAFE_MIRROR:-https://downloads.lightbend.com}
+
+    install_app \
+      "${TYPESAFE_MIRROR}/zinc/${ZINC_VERSION}" \
+      "zinc-${ZINC_VERSION}.tgz" \
+      "${zinc_path}"
+    ZINC_BIN="${_DIR}/${zinc_path}"
+  fi
 }
 
 # Determine the Scala version from the root pom.xml file, set the Scala URL,