Update appveyor to also try building dynamic loader.

Author: rpavlik

.appveyor.yml

@@ -39,7 +39,9 @@ install:
 build_script:
 - cmd: >-
     call "C:\\Program Files (x86)\\Microsoft Visual Studio\\2017\\Community\\VC\\Auxiliary\\Build\\%VCVARS%.bat" &&
-    cmake -GNinja -Bbuild -H. -DCMAKE_BUILD_TYPE=Release -DPYTHON_EXECUTABLE=C:/Python37-x64/python.exe &&
-    cd build &&
-    ninja &&
-    cd ..
+    cmake -GNinja -Bbuild -H. -DCMAKE_BUILD_TYPE=RelWithDebInfo -DPYTHON_EXECUTABLE=C:/Python37-x64/python.exe &&
+    ninja -C build
+- cmd: >-
+    call "C:\\Program Files (x86)\\Microsoft Visual Studio\\2017\\Community\\VC\\Auxiliary\\Build\\%VCVARS%.bat" &&
+    cmake -GNinja -Bbuild -H. -DCMAKE_BUILD_TYPE=RelWithDebInfo -DDYNAMIC_LOADER=ON -DPYTHON_EXECUTABLE=C:/Python37-x64/python.exe &&
+    ninja -C build