Build all tasks, regardless of target (dotnet#55346)

In a dirty tree, different architectures require different tasks.

For example,
```
./build.sh --os iossimulator -c Release
./build.sh --os android -c Release
```
the second step will complain that the AndroidAppBuilder task does not exist,
because the build-semaphore.txt was created during the first build which built
the AppleAppBuilder, but not the AndroidAppBuilder.

The solution is to build all the tasks, regardless of target

Simplifies building for different targets from the same dirty tree.  All the
tasks are always built once and then remain unchanged as long as their sources
don't change.

src/tasks/AppleAppBuilder/AppleAppBuilder.cs

@@ -161,7 +161,7 @@ public override bool Execute()
             throw new ArgumentException($"MainLibraryFileName='{MainLibraryFileName}' was not found in AppDir='{AppDir}'");
         }
 
-        if (ProjectName.Contains(" "))
+        if (ProjectName.Contains(' '))
         {
             throw new ArgumentException($"ProjectName='{ProjectName}' should not contain spaces");
         }

src/tasks/tasks.proj

@@ -1,18 +1,6 @@
 <Project Sdk="Microsoft.Build.Traversal">
   <ItemGroup>
     <ProjectReference Include="$(MSBuildThisFileDirectory)**\*.csproj" />
-    <ProjectReference Remove="$(MSBuildThisFileDirectory)AndroidAppBuilder\AndroidAppBuilder.csproj"
-                      Condition="'$(TargetOS)' != 'Android'" />
-    <ProjectReference Remove="$(MSBuildThisFileDirectory)AppleAppBuilder\AppleAppBuilder.csproj"
-                      Condition="'$(TargetOS)' != 'MacCatalyst' and '$(TargetOS)' != 'iOS' and '$(TargetOS)' != 'iOSSimulator' and '$(TargetOS)' != 'tvOS' and '$(TargetOS)' != 'tvOSSimulator'" />
-    <ProjectReference Remove="$(MSBuildThisFileDirectory)WasmAppBuilder\WasmAppBuilder.csproj"
-                      Condition="'$(TargetOS)' != 'Browser'" />
-    <ProjectReference Remove="$(MSBuildThisFileDirectory)WasmBuildTasks\WasmBuildTasks.csproj"
-                      Condition="'$(TargetOS)' != 'Browser'" />
-    <ProjectReference Remove="$(MSBuildThisFileDirectory)AotCompilerTask\MonoAOTCompiler.csproj"
-                      Condition="'$(TargetsMobile)' != 'true'" />
-    <ProjectReference Remove="$(MSBuildThisFileDirectory)RuntimeConfigParser\RuntimeConfigParser.csproj"
-                      Condition="'$(TargetsMobile)' != 'true'" />
   </ItemGroup>
 
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