CmdPal: Replace assembly metadata attributes with preprocessor directives (#44707)

## Summary of the Pull Request

This PR replaces custom metadata attributes used to pass build-time
information with preprocessor directives. It appears that metadata can
be stripped from the final build output, even though it survived AOT in
earlier tests on the main and stable branches.

New preprocesor directives in Microsoft.CmdPal.UI:
- `BUILD_INFO_PUBLISH_AOT` - when `PublishAot` MSBuild parameter is
`true`
- `BUILD_INFO_PUBLISH_TRIMMED `- when `PublishTrimmed` MSBuild parameter
is `true`
- `BUILD_INFO_CIBUILD `- when `CIBuild` MSBuild parameter is `true`

Using preprocessor directives avoids this uncertainty and provides a
more reliable solution.

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## PR Checklist

- [x] Closes: #44641
<!-- - [ ] Closes: #yyy (add separate lines for additional resolved
issues) -->
- [ ] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [ ] **Tests:** Added/updated and all pass
- [ ] **Localization:** All end-user-facing strings can be localized
- [ ] **Dev docs:** Added/updated
- [ ] **New binaries:** Added on the required places
- [ ] [JSON for
signing](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ESRPSigning_core.json)
for new binaries
- [ ] [WXS for
installer](https://github.com/microsoft/PowerToys/blob/main/installer/PowerToysSetup/Product.wxs)
for new binaries and localization folder
- [ ] [YML for CI
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ci/templates/build-powertoys-steps.yml)
for new test projects
- [ ] [YML for signed
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/release.yml)
- [ ] **Documentation updated:** If checked, please file a pull request
on [our docs
repo](https://github.com/MicrosoftDocs/windows-uwp/tree/docs/hub/powertoys)
and link it here: #xxx

<!-- Provide a more detailed description of the PR, other things fixed,
or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments

<!-- Describe how you validated the behavior. Add automated tests
wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed

src/modules/cmdpal/Microsoft.CmdPal.UI/Helpers/BuildInfo.cs

@@ -2,7 +2,6 @@
 // The Microsoft Corporation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System.Reflection;
 using System.Runtime.CompilerServices;
 
 namespace Microsoft.CmdPal.UI.Helpers;
@@ -18,19 +17,41 @@ internal static class BuildInfo
     // Runtime AOT detection
     public static bool IsNativeAot => !RuntimeFeature.IsDynamicCodeSupported;
 
-    // From assembly metadata (build-time values)
-    public static bool PublishTrimmed => GetBoolMetadata("PublishTrimmed", false);
+    // build-time values
+    public static bool PublishTrimmed
+    {
+        get
+        {
+#if BUILD_INFO_PUBLISH_TRIMMED
+          return true;
+#else
+            return false;
+#endif
+        }
+    }
 
-    // From assembly metadata (build-time values)
-    public static bool PublishAot => GetBoolMetadata("PublishAot", false);
+    // build-time values
+    public static bool PublishAot
+    {
+        get
+        {
+#if BUILD_INFO_PUBLISH_AOT
+            return true;
+#else
+            return false;
+#endif
+        }
+    }
 
-    public static bool IsCiBuild => GetBoolMetadata("CIBuild", false);
-
-    private static string? GetMetadata(string key) =>
-        Assembly.GetExecutingAssembly()
-            .GetCustomAttributes<AssemblyMetadataAttribute>()
-            .FirstOrDefault(a => a.Key == key)?.Value;
-
-    private static bool GetBoolMetadata(string key, bool defaultValue) =>
-        bool.TryParse(GetMetadata(key), out var result) ? result : defaultValue;
+    public static bool IsCiBuild
+    {
+        get
+        {
+#if BUILD_INFO_CIBUILD
+            return true;
+#else
+            return false;
+#endif
+        }
+    }
 }

src/modules/cmdpal/Microsoft.CmdPal.UI/Microsoft.CmdPal.UI.csproj

@@ -53,7 +53,7 @@
 
   <PropertyGroup>
     <!-- This disables the auto-generated main, so we can be single-instanced -->
-    <DefineConstants>DISABLE_XAML_GENERATED_MAIN</DefineConstants>
+    <DefineConstants>$(DefineConstants);DISABLE_XAML_GENERATED_MAIN</DefineConstants>
   </PropertyGroup>
 
   <!-- BODGY: XES Versioning and WinAppSDK get into a fight about the app manifest, which breaks WinAppSDK. -->
@@ -291,24 +291,15 @@
   </ItemGroup>
   <!-- </AdaptiveCardsWorkaround> -->
 
-  <!-- Metadata for build information  -->
-  <ItemGroup>
-    <AssemblyAttribute Include="System.Reflection.AssemblyMetadataAttribute">
-      <_Parameter1>PublishTrimmed</_Parameter1>
-      <_Parameter2>$(PublishTrimmed)</_Parameter2>
-    </AssemblyAttribute>
-    <AssemblyAttribute Include="System.Reflection.AssemblyMetadataAttribute">
-      <_Parameter1>PublishAot</_Parameter1>
-      <_Parameter2>$(PublishAot)</_Parameter2>
-    </AssemblyAttribute>
-    <AssemblyAttribute Include="System.Reflection.AssemblyMetadataAttribute">
-      <_Parameter1>CIBuild</_Parameter1>
-      <_Parameter2>$(CIBuild)</_Parameter2>
-    </AssemblyAttribute>
-    <AssemblyAttribute Include="System.Reflection.AssemblyMetadataAttribute">
-      <_Parameter1>CommandPaletteBranding</_Parameter1>
-      <_Parameter2>$(CommandPaletteBranding)</_Parameter2>
-    </AssemblyAttribute>
-  </ItemGroup>
+  <!-- Build information  -->
+  <PropertyGroup Condition=" '$(PublishAot)' == 'true' ">
+	<DefineConstants>$(DefineConstants);BUILD_INFO_PUBLISH_AOT</DefineConstants>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(PublishTrimmed)' == 'true' ">
+    <DefineConstants>$(DefineConstants);BUILD_INFO_PUBLISH_TRIMMED</DefineConstants>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(CIBuild)' == 'true' ">
+    <DefineConstants>$(DefineConstants);BUILD_INFO_CIBUILD</DefineConstants>
+  </PropertyGroup>
 
 </Project>