minor update to fix msbuild condition to correct syntax
diff --git a/src/csharp/Grpc.Tools/build/_protobuf/Google.Protobuf.Tools.targets b/src/csharp/Grpc.Tools/build/_protobuf/Google.Protobuf.Tools.targets
index b1030ba..ad6725f 100644
--- a/src/csharp/Grpc.Tools/build/_protobuf/Google.Protobuf.Tools.targets
+++ b/src/csharp/Grpc.Tools/build/_protobuf/Google.Protobuf.Tools.targets
@@ -137,7 +137,7 @@
<ProtoRoot>%(RelativeDir)</ProtoRoot>
</Protobuf_Compile>
<!-- Remove files not for compile. -->
- <Protobuf_Compile Remove="@(Protobuf_Compile)" Condition=" !%(ProtoCompile) " />
+ <Protobuf_Compile Remove="@(Protobuf_Compile)" Condition=" '%(ProtoCompile)' != 'true' " />
<!-- Ensure invariant Source=%(Identity). -->
<Protobuf_Compile>
<Source>%(Identity)</Source>