Handle ${SLOEBER_HOME} properly for the boards.txt file

When reading the cfg file the ${SLOEBER_HOME) (if present) was not
properly processed.
This change also makes sure the SLOBER_HOME variable is there if it
needs to be (It went from string replacement to pat.isPrefix)
Hopefully this fixes the github build

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

@@ -697,7 +697,7 @@ public BoardDescription(Map<String, String> envVars) {
                 myBoardID = value;
                 break;
             case KEY_SLOEBER_BOARD_TXT:
-                myUserSelectedBoardsTxtFile = new File(value);
+                myUserSelectedBoardsTxtFile = resolvePathEnvironmentString(new File(value));
                 mySloeberBoardTxtFile = new BoardTxtFile(myUserSelectedBoardsTxtFile);
                 break;
             case KEY_SLOEBER_UPLOAD_PORT:
@@ -822,7 +822,7 @@ public Map<String, String> getEnvVars() {
         }
         allVars.put(ENV_KEY_SOFTWARE,VENDOR_ARDUINO);
         allVars.put(ENV_KEY_ID,getBoardID());
-        
+
 
 
         allVars.put(ENV_KEY_SERIAL_PORT, getActualUploadPort());

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

@@ -228,16 +228,15 @@ public static IPath getWorkspaceRoot() {
      * Check whether the string starts with the SLOEBER_HOME path If it does replace
      * with environment variable This keeps things more compatible over environments
      *
-     * @param path
+     * @param file
      *            string to check
      * @return modified string or the original
      */
-    public static String makePathEnvironmentString(IPath path) {
-        return path.toOSString().replace(sloeberHomePathToString, SLOEBER_HOME_VAR);
-    }
-
     public static String makePathVersionString(File file) {
-        return file.getPath().replace(sloeberHomePathToString, SLOEBER_HOME_VAR);
+    	if(sloeberHomePath.isPrefixOf(IPath.fromFile(file))) {
+    		return SLOEBER_HOME_VAR+SLACH+IPath.fromFile(file) .makeRelativeTo(sloeberHomePath).toString();
+    	}
+        return file.toString();
     }
 
     /**
@@ -247,7 +246,13 @@ public static String makePathVersionString(File file) {
      * @return
      */
     public static File resolvePathEnvironmentString(File file) {
-        String retString = file.getPath().replace(SLOEBER_HOME_VAR, sloeberHomePathToString);
+
+        String retString = file.getPath();
+        if (retString.startsWith(SLOEBER_HOME_VAR)) {
+        	retString=retString.replace(SLOEBER_HOME_VAR, EMPTY_STRING);
+        	return sloeberHomePath.append(retString).toFile();
+        	//.replace(SLOEBER_HOME_VAR, sloeberHomePathToString);
+        }
         return new File(retString);
     }