merge 0.6.8

.circleci/build_win.ps1

@@ -0,0 +1,18 @@
+$ErrorActionPreference = "Stop"
+
+cd "$PSScriptRoot\.."
+
+if ("$Env:FORCE_RELEASE" -Or "$Env:CIRCLE_TAG") {
+	New-Item prerelease.txt -type file
+	Write-Host "Building release version."
+}
+
+mkdir build
+cd build
+$boost_dir=(Resolve-Path $PSScriptRoot\..\deps\boost\lib\cmake\Boost-*)
+..\deps\cmake\bin\cmake -G "Visual Studio 16 2019" -DBoost_DIR="$boost_dir\" -DCMAKE_MSVC_RUNTIME_LIBRARY=MultiThreaded -DCMAKE_INSTALL_PREFIX="$PSScriptRoot\..\upload" ..
+if ( -not $? ) { throw "CMake configure failed." }
+msbuild solidity.sln /p:Configuration=Release /m:5 /v:minimal
+if ( -not $? ) { throw "Build failed." }
+..\deps\cmake\bin\cmake --build . -j 5 --target install --config Release
+if ( -not $? ) { throw "Install target failed." }