Fix errors in the binary-release Windows build script

I still had no chance to try this on CircleCI, but manually following the
instructions revealed these errors.
Also explicitly specify the compile toolchain on linux, so the script is
not so much dependent on what shows up in the environment.

tools/build/binary-release/build-linux.sh

@@ -19,7 +19,7 @@ tar -xzf rakudo.tgz
 cd rakudo-*
 
 # Build Rakudo
-perl Configure.pl --gen-moar --gen-nqp --backends=moar --relocatable
+perl Configure.pl --gen-moar --gen-nqp --backends=moar --moar-option='--toolchain=gnu' --relocatable
 make
 make install
 

tools/build/binary-release/build-windows.ps1

@@ -35,7 +35,7 @@ cd rakudo-*
 
 # Build Rakudo
 
-perl Configure.pl --gen-moar --gen-nqp --backends=moar --relocatable
+perl Configure.pl --gen-moar --gen-nqp --backends=moar --moar-option='--toolchain=msvc' --relocatable
 CheckLastExitCode
 nmake install
 CheckLastExitCode
@@ -54,16 +54,15 @@ CheckLastExitCode
 cd zef
 ..\install\bin\raku.exe -I. bin\zef install .
 CheckLastExitCode
+cd ..
 
 
 # Prepare the package
 
-cp -r "tools\build\binary-release\Windows\*" install
+cp -Force -r "tools\build\binary-release\Windows\*" install
 cp LICENSE install
 
-$version = Get-Content -Path .\VERSION -Raw
-$version = $version.Trim()
-mv install rakudo-$version
+mv install rakudo-$Env:VERSION
 
-Compress-Archive -Path rakudo-$version -DestinationPath ..\rakudo-win.zip
+Compress-Archive -Path rakudo-$Env:VERSION -DestinationPath ..\rakudo-win.zip