[SL.Core] Use release build for code coverage.

tests/CodeCoverage/CodeCoverage.cmd

@@ -7,12 +7,10 @@ nuget restore packages.config -PackagesDirectory .
 cd ..
 cd ..
 
-dotnet restore  SixLabors.Core.sln
-dotnet build  SixLabors.Core.sln --no-incremental -c debug /p:codecov=true
- 
-rem The -threshold options prevents this taking ages...
-rem tests\CodeCoverage\OpenCover.4.6.519\tools\OpenCover.Console.exe -target:"dotnet.exe" -targetargs:"test tests\SixLabors.Shapes.Tests\SixLabors.Shapes.Tests.csproj --no-build -c Release /p:codecov=true" -threshold:10 -register:user -filter:"+[SixLabors.Shapes*]*" -excludebyattribute:*.ExcludeFromCodeCoverage* -hideskipped:All -returntargetcode -output:.\SixLabors.Shapes.Coverage.xml
-tests\CodeCoverage\OpenCover.4.6.519\tools\OpenCover.Console.exe -target:"dotnet.exe" -targetargs:"test tests\SixLabors.Core.Tests\SixLabors.Core.Tests.csproj --no-build -c debug" -searchdirs:"tests\SixLabors.Core.Tests\bin\Release\netcoreapp1.1" -register:user -output:.\SixLabors.Core.Coverage.xml -hideskipped:All -returntargetcode -oldStyle -filter:"+[SixLabors.*]*" 
+dotnet restore SixLabors.Core.sln
+dotnet build SixLabors.Core.sln --no-incremental -c release /p:codecov=true
+
+tests\CodeCoverage\OpenCover.4.6.519\tools\OpenCover.Console.exe -target:"dotnet.exe" -targetargs:"test tests\SixLabors.Core.Tests\SixLabors.Core.Tests.csproj --no-build -c release" -searchdirs:"tests\SixLabors.Core.Tests\bin\Release\netcoreapp1.1" -register:user -output:.\SixLabors.Core.Coverage.xml -hideskipped:All -returntargetcode -oldStyle -filter:"+[SixLabors.*]*" 
 
 if %errorlevel% neq 0 exit /b %errorlevel%