Static web asset building is not incremental

[jjonescz]

SDK version: 10p5 or local build (feb621b)
Steps to reproduce:

1. dotnet new blazorwasm
2. dotnet build
3. dotnet build -bl -question

Expected: success
Actual: fails with

MSBUILD : error : Building target "_BuildCopyStaticWebAssetsPreserveNewest" partially, because some output files are out of date with respect to their input files.

And in the binlog I can see the problem is obj\Debug\net10.0\dotnet.js.

[MackinnonBuck]

cc @javiercn