payara: require Java 8 specifically

Formula/payara.rb

@@ -6,7 +6,7 @@ class Payara < Formula
 
   bottle :unneeded
 
-  depends_on :java => "1.7+"
+  depends_on :java => "1.8"
 
   conflicts_with "glassfish", :because => "both install the same scripts"
 
@@ -18,7 +18,8 @@ class Payara < Formula
                              "AS_INSTALL=#{libexec}/glassfish"
 
     libexec.install Dir["*"]
-    bin.install_symlink Dir["#{libexec}/bin/*"]
+    bin.install Dir["#{libexec}/bin/*"]
+    bin.env_script_all_files(libexec/"bin", Language::Java.java_home_env("1.8"))
   end
 
   def caveats; <<~EOS