[APPVEYOR] Clean up our build logs so we can focus on warnings and errors.

appveyor.yml

@@ -27,8 +27,10 @@ build_script:
   - md c:\ros_build
   - cd c:\ros_build
   - call %APPVEYOR_BUILD_FOLDER%\configure.cmd %clang_configure_option% -DENABLE_ROSTESTS=1
-  - ninja -k0
-  - ninja bootcd
+  - ps: >-
+      & ninja -k0 2>&1 | select-string -pattern "\[\d+\/\d+\] " -NotMatch | %{$_.Line}
+  - ps: >-
+      & ninja bootcd 2>&1 | select-string -pattern "\[\d+\/\d+\] " -NotMatch | %{$_.Line}
 
 test: off
 deploy: off