[release/10.0] Fix path separator issue on Linux/macOS in dotnet-ef tools

[Copilot]

Description
MSBuild returns Windows-style backslashes in the OutputPath property (e.g., bin\Debug\net10.0\), even when running on Linux/macOS. When this path is combined with the ProjectDir path using Path.Combine and Path.GetFullPath, the resulting path contains backslashes on non-Windows platforms. This causes incorrect directory creation (e.g., a directory named bin\Debug instead of bin/Debug) which then leads to build failures when subsequent operations try to find files using the correct platform-specific paths.
There was logic to normalize this, but it wasn't applied to the BuildHost target folder.

Customer impact
Any customer using dotnet-ef tools 10.0.2 on Linux/macOS will encounter build failures when running dotnet ef.
The workaround is to first build the project using dotnet build and then use the --no-build option when running EF commands.

How found
Multiple customer reports on 10.0.2.

Regression
Yes, from 10.0.1. Introduced in PR #37301 which added an msbuild invocation to get the target framework.

Testing
Tested manually

Risk
Low. Targeted fix that applies the existing logic consistently. Only affects design-time tools.

Original prompt

Investigate #37506. Start by creating a project that reproduces the reported issue, after that try to isolate it to a test case. If it's not possible to create a test case for this issue just keep the project in the PR and try to fix the issue.

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[AndriySvyryd]

@copilot Also move the similar path-normalizing logic from RootCommand.cs to this file so that it's applied consistently

[Copilot]

Moved the path normalization to Project.FromFile() where the OutputPath property is set. This normalizes the path once at the source, so RootCommand.cs no longer needs its own normalization logic. Commit: 8796083

[AndriySvyryd]

@copilot Update progress by rewriting the PR summary using this template:

Fixes #{number}

**Description**
{Issue description}

**Customer impact**
{How does the reported issue affects customer's app? Are there workarounds?}

**How found**
{Was it customer reported or found during verification? How many customers are affected?}

**Regression**
{Is it a regression from a released version? Which one?}

**Testing**
{How the changes were tested}

**Risk**
{Low/Medium/High, argument why}

[Copilot]

@copilot Update progress by rewriting the PR summary using this template:

...

Updated the PR description with the servicing template.

[Copilot]

Pull request overview

This PR fixes a critical path separator issue in the dotnet-ef command-line tools on Linux/macOS. MSBuild returns Windows-style backslashes in the OutputPath property even on non-Windows platforms, which causes incorrect directory creation and subsequent build failures. The fix normalizes the path separator earlier in the pipeline (when reading from MSBuild in Project.cs) rather than at usage points, ensuring all consumers receive correctly-normalized paths.

Changes:

• Moved path separator normalization from RootCommand.cs to Project.cs where the OutputPath is first read from MSBuild
• Normalized OutputPath is now stored in the Project object, eliminating the need for normalization at usage points
• Fixed the CopyBuildHost operation which was previously receiving paths with incorrect separators

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/dotnet-ef/RootCommand.cs	Removed redundant path separator normalization since OutputPath is now normalized upstream
src/dotnet-ef/Project.cs	Added path separator normalization when reading OutputPath from MSBuild and storing it in the Project object