try just converting the \ to a /

CI/before_script.msvc.sh

@@ -417,8 +417,7 @@ fi
 		# Boost's installer is still based on ms-dos API that doesn't support larger than 260 char path names
 		# We work around this by installing to root of the current working drive and then move it to our deps
 		# get the current working drive's root, we'll install to that temporarily
-		CWD_DRIVE_ROOT=$(powershell -command '(get-location).Drive.Root')
-		
+		CWD_DRIVE_ROOT=$(echo "$(powershell -command '(get-location).Drive.Root')" | sed "s,\\\\,/,g") 
 		
 		if [ -d Boost ] && grep "BOOST_VERSION 106700" Boost/boost/version.hpp > /dev/null; then
 			printf "Exists. "