Fix dotnet/coreclr#24867 (dotnet/coreclr#24870)

Pre SDK 3.0, a project type that is not .csproj would not include Directory.Build.targets. Change empty.proj to empty.csproj to allow source build, which uses a 2.1 sdk to build, correctly import Directory.Build.targets.

Commit migrated from c6d6fc20a5

eng/build-job.yml

@@ -131,7 +131,7 @@ jobs:
 
     # Sign on Windows
     - ${{ if and(ne(variables['System.TeamProject'], 'public'), ne(variables['Build.Reason'], 'PullRequest'), eq(parameters.osGroup, 'Windows_NT')) }}:
-      - script: powershell eng\common\build.ps1 -ci -sign -restore -configuration:$(buildConfig) -warnaserror:0 /p:ArcadeBuild=true /p:OfficialBuild=true /p:BuildOS=$(osGroup) /p:BuildArch=$(archType) /p:BuildType=$(buildConfigUpper) /p:DotNetSignType=%_SignType% -projects $(Build.SourcesDirectory)\eng\empty.proj
+      - script: powershell eng\common\build.ps1 -ci -sign -restore -configuration:$(buildConfig) -warnaserror:0 /p:ArcadeBuild=true /p:OfficialBuild=true /p:BuildOS=$(osGroup) /p:BuildArch=$(archType) /p:BuildType=$(buildConfigUpper) /p:DotNetSignType=%_SignType% -projects $(Build.SourcesDirectory)\eng\empty.csproj
         displayName: Sign Binaries
 
       - task: PublishBuildArtifacts@1
@@ -168,7 +168,7 @@ jobs:
     # Publish official build
     - ${{ if and(ne(variables['System.TeamProject'], 'public'), ne(variables['Build.Reason'], 'PullRequest')) }}:
       - ${{ if ne(parameters.osGroup, 'Windows_NT') }}:
-        - script: ./eng/common/build.sh /p:DotNetPublishToBlobFeed=true --ci --restore --projects $(Build.SourcesDirectory)/eng/empty.proj
+        - script: ./eng/common/build.sh /p:DotNetPublishToBlobFeed=true --ci --restore --projects $(Build.SourcesDirectory)/eng/empty.csproj
           displayName: Restore blob feed tasks
           ${{ if eq(parameters.osGroup, 'FreeBSD') }}:
             env:
@@ -184,7 +184,7 @@ jobs:
               DotNetCoreSdkDir: /usr/local/dotnet
       - ${{ if eq(parameters.osGroup, 'Windows_NT') }}:
         # TODO: pass publish feed url and access token in from the internal pipeline
-        - powershell: eng\common\build.ps1 /p:DotNetPublishToBlobFeed=true -ci -restore -projects $(Build.SourcesDirectory)\eng\empty.proj
+        - powershell: eng\common\build.ps1 /p:DotNetPublishToBlobFeed=true -ci -restore -projects $(Build.SourcesDirectory)\eng\empty.csproj
           displayName: Restore blob feed tasks
         - powershell: eng\common\msbuild.ps1 -ci src\publishwitharcade.proj /p:__BuildType=$(buildConfigUpper) /p:__BuildArch=$(archType) /p:OSIdentifier=$(osIdentifier) /p:AzureFeedUrl=$(dotnetfeedUrl) /p:AzureAccountKey=$(dotnetfeedPAT)
           displayName: Publish packages to blob feed

eng/send-to-helix-step.yml

@@ -20,7 +20,7 @@ parameters:
 steps:
 - ${{ if eq(parameters.osGroup, 'Windows_NT') }}:
   # TODO: Remove and consolidate this when we move to arcade via init-tools.cmd.
-  - powershell: eng\common\build.ps1 /p:DotNetPublishToBlobFeed=true -ci -restore -projects $(Build.SourcesDirectory)\eng\empty.proj
+  - powershell: eng\common\build.ps1 /p:DotNetPublishToBlobFeed=true -ci -restore -projects $(Build.SourcesDirectory)\eng\empty.csproj
     displayName: Restore blob feed tasks
     ${{ if ne(parameters.condition, '') }}:
       condition: ${{ parameters.condition }}
@@ -51,7 +51,7 @@ steps:
 
 - ${{ if ne(parameters.osGroup, 'Windows_NT') }}:
   # TODO: Remove and consolidate this when we move to arcade via init-tools.sh.
-  - script: ./eng/common/build.sh /p:DotNetPublishToBlobFeed=true --ci --restore --projects $(Build.SourcesDirectory)/eng/empty.proj
+  - script: ./eng/common/build.sh /p:DotNetPublishToBlobFeed=true --ci --restore --projects $(Build.SourcesDirectory)/eng/empty.csproj
     displayName: Restore blob feed tasks
     ${{ if ne(parameters.condition, '') }}:
       condition: ${{ parameters.condition }}

src/coreclr/build-test.sh

@@ -490,7 +490,7 @@ build_native_projects()
         __versionSourceFile="$intermediatesForBuild/version.c"
         if [ $__SkipGenerateVersion == 0 ]; then
             pwd
-            $__ProjectRoot/eng/common/msbuild.sh $__ProjectRoot/eng/empty.proj \
+            $__ProjectRoot/eng/common/msbuild.sh $__ProjectRoot/eng/empty.csproj \
                                                  /p:NativeVersionFile=$__versionSourceFile \
                                                  /p:ArcadeBuild=true /t:GenerateNativeVersionFile /restore \
                                                  $__CommonMSBuildArgs $__UnprocessedBuildArgs

src/coreclr/build.cmd

@@ -362,7 +362,7 @@ REM ============================================================================
 @if defined _echo @echo on
 
 powershell -NoProfile -ExecutionPolicy ByPass -NoLogo -File "%__ProjectDir%\eng\common\msbuild.ps1"^
-    %__ProjectDir%\eng\empty.proj /p:NativeVersionFile="%__RootBinDir%\obj\_version.h"^
+    %__ProjectDir%\eng\empty.csproj /p:NativeVersionFile="%__RootBinDir%\obj\_version.h"^
     /p:ArcadeBuild=true /t:GenerateNativeVersionFile /restore^
     %__CommonMSBuildArgs% %__UnprocessedBuildArgs%
 if not !errorlevel! == 0 (

src/coreclr/build.sh

@@ -230,7 +230,7 @@ build_native()
         __versionSourceFile="$intermediatesForBuild/version.c"
         if [ $__SkipGenerateVersion == 0 ]; then
             pwd
-            "$__ProjectRoot/eng/common/msbuild.sh" $__ProjectRoot/eng/empty.proj \
+            "$__ProjectRoot/eng/common/msbuild.sh" $__ProjectRoot/eng/empty.csproj \
                                         /p:NativeVersionFile=$__versionSourceFile \
                                         /p:ArcadeBuild=true /t:GenerateNativeVersionFile /restore \
                                         $__CommonMSBuildArgs $__UnprocessedBuildArgs