GithubCI: build the whole solution in macOS&Linux too

Now that we have removed the only VS-specific project [1],
we can make all pipelines of all OSs consistent, building
the solution instead of a specific project.

[1] 90e16c1b1e

.github/workflows/CI.yml

@@ -8,43 +8,43 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v2
-      
+
     - name: Download latest NuGet 
       run: wget $NUGET_URL
 
     - name: Install Dependencies
       run: mono nuget.exe restore src/TgSharp.sln
-    
+
     - name: Build Project
-      run: xbuild src/TgSharp.Core/TgSharp.Core.csproj
-      
+      run: xbuild src/TgSharp.sln
+
   macos:
     runs-on: macos-latest
     steps:
     - uses: actions/checkout@v2
-      
+
     - name: Download latest NuGet
       run:  curl -o nuget.exe $NUGET_URL
 
     - name: Install Dependencies
       run: mono nuget.exe restore src/TgSharp.sln
-      
+
     - name: Build Project
-      run: MSBuild src/TgSharp.Core/TgSharp.Core.csproj
+      run: msbuild src/TgSharp.sln
 
   windows:
     runs-on: windows-latest
     steps:
     - uses: actions/checkout@v2
-    
+
     - name: Download Nuget.exe
       run: Invoke-WebRequest -OutFile Nuget.exe $Env:NUGET_URL
-      
+
     - name: Install Dependencies
       run: ./Nuget.exe restore src/TgSharp.sln
-    
+
     - name: setup-msbuild
       uses: microsoft/setup-msbuild@v1
-      
+
     - name: Build Project
       run: MSBuild src/TgSharp.sln