Fix the solution directory detection on individual project build (#64)

Author: AlexUstinov

Directory.Build.props

@@ -22,7 +22,8 @@
 
   <PropertyGroup>
     <TargetFramework>netcoreapp3.1</TargetFramework>
-    <SolutionDir Condition="$(SolutionDir) == ''">$(MSBuildThisFileDirectory.TrimEnd('\').TrimEnd('/'))\</SolutionDir>
+    <SolutionDir Condition="$(SolutionDir) == ''">$([MSBuild]::EnsureTrailingSlash(
+      $([MSBuild]::GetDirectoryNameOfFileAbove('$(MSBuildThisFileDirectory)', 'Orm.sln'))))</SolutionDir>
     <Configuration Condition="$(Configuration) == ''">Debug</Configuration>
     <AllowedOutputExtensionsInPackageBuildOutputFolder>$(AllowedOutputExtensionsInPackageBuildOutputFolder);.pdb</AllowedOutputExtensionsInPackageBuildOutputFolder>
     <NoLogo>true</NoLogo>

Extensions/Directory.Build.props

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
-  <Import Project="$(SolutionDir)Directory.Build.props" />
+  <Import Project="$([MSBuild]::GetPathOfFileAbove('Directory.Build.props', '$(MSBuildThisFileDirectory)../'))" />
   <PropertyGroup>
     <ExtensionsKeyFile>$(MSBuildThisFileDirectory)Extensions.snk</ExtensionsKeyFile>
   </PropertyGroup>