[TD]fix errors in MS CI

- apparently the "or" alternative to "||" is not supported
  by MS but is part of the c++ specification:
  https://en.cppreference.com/w/cpp/language/operator_alternative

- also missing TechDrawExport

src/Mod/TechDraw/App/LineGenerator.cpp

@@ -127,7 +127,7 @@ QPen LineGenerator::getLinePen(size_t lineNumber, double nominalLineWidth)
     // there are some lines with numbers >1 that are also continuous, and
     // a dash pattern is not applicable.
     std::string naToken{"n/a"};
-    if (elements.empty() or elements.front() == naToken) {
+    if (elements.empty() || elements.front() == naToken) {
         // plain boring solid line (or possibly an invalid line number)
         linePen.setStyle(Qt::SolidLine);
         return linePen;

src/Mod/TechDraw/App/LineGenerator.h

@@ -44,7 +44,7 @@
 
 namespace TechDraw {
 
-class LineGenerator {
+class TechDrawExport LineGenerator {
 public:
     LineGenerator();
     ~LineGenerator() = default;