Adds JNI symbol check to ensure we don't miss any definitions (#160)

toolchains/linux.gradle

@@ -59,3 +59,29 @@ ext.debugStripSetup = {
         }
     }
 }
+
+ext.checkNativeSymbols = { getSymbolFunc ->
+    project.tasks.whenObjectAdded { task ->
+        if (task.name.contains('link') && task.name.contains('SharedLibrary')) {
+            def library = task.outputFile.absolutePath
+            task.doLast {
+                def nmOutput = new ByteArrayOutputStream()
+                exec { 
+                    commandLine "nm", library
+                    standardOutput nmOutput
+                }
+                // Remove '\r' so we can check for full string contents
+                String nmSymbols = nmOutput.toString().replace('\r', '')
+
+                def symbolList = getSymbolFunc()
+                symbolList.each {
+                    //Add \n so we can check for the exact symbol
+                    def found = nmSymbols.contains(it + '\n')
+                    if (!found) {
+                        throw new GradleException("Found a definition that does not have a matching symbol ${it}")
+                    }
+                }
+            }
+        }
+    }
+}