Idegen: Don't assume a backslash is preceded by a space

Only remove a backslash, nothing more. Otherwise a line with just
a backslash will cause a crash.

Bug: 28218145
Change-Id: I540a2508ba1fbd3f03cf8258d1fe4b99e0472c88

tools/idegen/src/com/android/idegen/MakeFileParser.java

@@ -150,7 +150,7 @@ public class MakeFileParser {
                 lineBuffer.append(" ");
             }
             if (line.endsWith("\\")) {
-                lineBuffer.append(line.substring(0, line.length() - 2).trim());
+                lineBuffer.append(line.substring(0, line.length() - 1).trim());
             } else {
                 lineBuffer.append(line);
             }