Cause: Someone was calling <MSBuild Projects="Common.csproj" Properties="..." />
. Then, MSBuild thinks that it should build Common.csproj again with those different properties, and it happened to occur at the same time with the regular compilation of Common.csproj.
Fix: Call <MSBuild ... />
without those unneeded properties.
Test:
Common.targets
<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
<Target Name="Build">
<Message Importance="high" Text="Build in $(MSBuildThisFile)" />
</Target>
<Target Name="After" DependsOnTargets="Build">
<Message Importance="high" Text="After in $(MSBuildThisFile)" />
</Target>
</Project>
Other.targets
<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
<Target Name="Build">
<Message Importance="high" Text="Build in $(MSBuildThisFile)" />
<MSBuild Projects="common.targets" Targets="Build" /> <!-- regular builds -->
<MSBuild Projects="common.targets" <!-- custom invocation with properties -->
Targets="After"
Properties="myprop=myvalue"
/>
</Target>
</Project>
Run:
> msbuild other.targets /clp:verbosity=minimal
Build in other.targets
Build in common.targets
Build in common.targets <<<< Common.targets Build is invoked again
After in common.targets
And indeed, removing Properties="myprop=myvalue"
solves the issue.