Update zulu7.rb (#3173)

Update zulu7 to use `system_command`.

Casks/zulu7.rb

@@ -10,15 +10,20 @@ cask 'zulu7' do
   pkg "Double-Click to Install Zulu #{version.major}.pkg"
 
   postflight do
-    system '/usr/bin/sudo', '-E', '--',
-           '/bin/mv', '-f', '--', "/Library/Java/JavaVirtualMachines/zulu-#{version.major}.jdk", "/Library/Java/JavaVirtualMachines/zulu-#{version.before_comma}.jdk"
-    system '/usr/bin/sudo', '-E', '--',
-           '/bin/ln', '-nsf', '--', "/Library/Java/JavaVirtualMachines/zulu-#{version.before_comma}.jdk", "/Library/Java/JavaVirtualMachines/zulu-#{version.major}.jdk"
+    system_command '/bin/mv',
+                   args: ['-f', '--', "/Library/Java/JavaVirtualMachines/zulu-#{version.major}.jdk", "/Library/Java/JavaVirtualMachines/zulu-#{version.before_comma}.jdk"],
+                   sudo: true
+    system_command '/bin/ln',
+                   args: ['-nsf', '--', "/Library/Java/JavaVirtualMachines/zulu-#{version.before_comma}.jdk", "/Library/Java/JavaVirtualMachines/zulu-#{version.major}.jdk"],
+                   sudo: true
+
     if MacOS.version <= :mavericks
-      system '/usr/bin/sudo', '-E', '--',
-             '/bin/rm', '-rf', '--', '/System/Library/Frameworks/JavaVM.framework/Versions/CurrentJDK'
-      system '/usr/bin/sudo', '-E', '--',
-             '/bin/ln', '-nsf', '--', "/Library/Java/JavaVirtualMachines/zulu-#{version.before_comma}.jdk/Contents", '/System/Library/Frameworks/JavaVM.framework/Versions/CurrentJDK'
+      system_command '/bin/rm',
+                     args: ['-rf', '--', '/System/Library/Frameworks/JavaVM.framework/Versions/CurrentJDK'],
+                     sudo: true
+      system_command '/bin/ln',
+                     args: ['-nsf', '--', "/Library/Java/JavaVirtualMachines/zulu#{version.before_comma}.jdk/Contents", '/System/Library/Frameworks/JavaVM.framework/Versions/CurrentJDK'],
+                     sudo: true
     end
   end