#1339 env var build.system.path not properly set

due to removal of referenced.core.path which is actually the same as
runtime.platform.path
While investigating I also found code that was only partially updated

Author: jantje

io.sloeber.core/config/pre_processing_platform_default.txt

@@ -4,7 +4,7 @@ recipe.objcopy.hex.pattern=${recipe.objcopy.bin.pattern}
 archive_file=arduino.ar
 archive_file_path=${build.path}/${archive_file}
 runtime.ide.version=10812
-build.system.path=${referenced.core.path}${DirectoryDelimiter}system
+build.system.path=${runtime.platform.path}${DirectoryDelimiter}system
 serial.port=${com_port}
 build.project_name=${ProjName}
 

io.sloeber.core/src/io/sloeber/core/api/BoardsManager.java

@@ -569,27 +569,8 @@ public static Map<String, String> getEnvironmentVariables() {
         }
         myWorkbenchEnvironmentVariables.clear();
         ArduinoPlatformVersion latestAvrPlatform = getNewestInstalledPlatform(Const.ARDUINO, Const.AVR);
-        ArduinoPlatformVersion latestSamdPlatform = null;
-        ArduinoPlatformVersion latestSamPlatform = null;
-        for (ArduinoPlatformVersion curPlatform : getInstalledPlatforms()) {
-            ArduinoPackage pkg = curPlatform.getParent().getParent();
-            if (pkg != null) {
-                myWorkbenchEnvironmentVariables.putAll(Helpers.getEnvVarPlatformFileTools(curPlatform, false));
-                if (Const.ARDUINO.equalsIgnoreCase(pkg.getMaintainer())) {
-                    switch (curPlatform.getArchitecture()) {
-                    case Const.AVR:
-                        latestAvrPlatform = curPlatform;
-                        break;
-                    case Const.SAM:
-                        latestSamPlatform = curPlatform;
-                        break;
-                    case Const.SAMD:
-                        latestSamdPlatform = curPlatform;
-                        break;
-                    }
-                }
-            }
-        }
+        ArduinoPlatformVersion latestSamdPlatform = getNewestInstalledPlatform(Const.ARDUINO, Const.SAMD);
+        ArduinoPlatformVersion latestSamPlatform = getNewestInstalledPlatform(Const.ARDUINO, Const.SAM);
 
         if (latestSamdPlatform != null) {
             myWorkbenchEnvironmentVariables.putAll(Helpers.getEnvVarPlatformFileTools(latestSamdPlatform, false));