Make build.FullCLR.ps1 build RELEASE by default

Since we start include CRT runtime inside powershell.exe,
the size of executable jumped from 32kb to 1Mb in DEBUG.
Release produces about 20kb, so we keep size managable.

build.FullCLR.ps1

@@ -5,7 +5,12 @@ param(
         "Visual Studio 12 2013 Win64",
         "Visual Studio 14 2015", 
         "Visual Studio 14 2015 Win64")]
-    [string]$cmakeGenerator = ""
+    [string]$cmakeGenerator = "",
+
+    [ValidateSet(
+        "Debug",
+        "Release")] 
+    [string]$msbuildConfiguration = "Release"   
 )
 
 $origPWD = $pwd
@@ -67,9 +72,9 @@ try
     {
         cmake ..\src\powershell-native
     }
-    msbuild powershell.sln
+    msbuild powershell.sln /p:Configuration=$msbuildConfiguration
 
-    cp -rec Debug\* $BINFULL
+    cp -rec $msbuildConfiguration\* $BINFULL
 }
 finally
 {