Respect JAVACMD environment variable if it's set

This patch changes the launcher to respect the JAVACMD environment variable for
determining JVM launcher command.

Signed-off-by: Nick Sieger <[email protected]>

Author: penberg

spec/launcher_spec.rb

@@ -13,6 +13,16 @@
     jruby_launcher("-Xhelp 2>&1").should =~ /JRuby Launcher usage/
   end
 
+  it "should use $JAVACMD when JAVACMD is specified" do
+    with_environment "JAVACMD" => File.join("jato") do
+      if windows?
+        jruby_launcher_args("-v 2>&1").join.should =~ %r{jato}
+      else
+        jruby_launcher_args("-v").first.should == File.join("jato")
+      end
+    end
+  end
+
   it "should use $JAVA_HOME/bin/java when JAVA_HOME is specified" do
     with_environment "JAVA_HOME" => File.join("some", "java", "home") do
       if windows?

unixlauncher.cpp

@@ -38,12 +38,16 @@ int UnixLauncher::run(int argc, char* argv[], char* envp[]) {
 
     string java("");
 
-    if (!jdkhome.empty()) {
-        java = jdkhome + "/bin/java";
-    } else if (getenv("JAVA_HOME") != NULL) {
-        java = string(getenv("JAVA_HOME")) + "/bin/java";
+    if (getenv("JAVACMD") != NULL) {
+        java = getenv("JAVACMD");
     } else {
-        java = findOnPath("java");
+        if (!jdkhome.empty()) {
+            java = jdkhome + "/bin/java";
+        } else if (getenv("JAVA_HOME") != NULL) {
+            java = string(getenv("JAVA_HOME")) + "/bin/java";
+        } else {
+            java = findOnPath("java");
+        }
     }
 
     if (java.empty()) {