Windows: add MSYS2 install scripts

images/win/scripts/Installers/Install-MSYS2.ps1

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+################################################################################
+##  File:  Install-MSYS2.ps1
+##  Desc:  Install MSYS2 and 64-bit gcc, cmake, & llvm (32-bit commented out)
+################################################################################
+
+# References
+# https://github.com/msys2/MINGW-packages/blob/master/azure-pipelines.yml
+# https://packages.msys2.org/group/
+
+$dash = "—"
+$wid = 80
+
+$orig_path = $env:PATH
+$git_path  = "C:\Program Files\Git"
+
+# get info from https://sourceforge.net/projects/msys2/files/Base/x86_64/
+$msy2_uri  = "http://repo.msys2.org/distrib/x86_64/msys2-base-x86_64-20190524.tar.xz"
+$msy2_sha1 = "cfe5035b1b81b43469d16bfc23be8006b9a44455".ToUpper()
+
+$msy2_file = "$env:AGENT_TEMPDIRECTORY/msys2.tar.xz".replace('\', '/')
+
+# Download the latest msys2 x86_64
+Write-Host Starting download
+Invoke-WebRequest -UseBasicParsing -Uri $msy2_uri -OutFile $msy2_file
+Write-Host Finished download
+
+# check SHA1
+$dl_sha1 = (Get-FileHash -Path $msy2_file -Algorithm SHA1).Hash
+
+if ($dl_sha1 -ne $msy2_sha1) {
+  Write-Host "SHA1 mismatch, exiting"
+  exit 1
+}
+
+$msy2_file_u = "/$msy2_file".replace(':', '')
+
+# git has tar.exe in usr/bin, but xz.exe is in mingw64/bin
+$env:PATH = "$git_path\mingw64\bin;$orig_path"
+$tar      = "$git_path\usr\bin\tar.exe"
+
+# extract tar.xz to C:\
+&$tar -Jxf $msy2_file_u -C /c/
+
+Remove-Item $msy2_file
+
+Write-Host Finished extraction
+
+$env:PATH = "C:\msys64\mingw64\bin;C:\msys64\usr\bin;$orig_path"
+
+$ErrorActionPreference = "Continue"
+
+Write-Host " bash.exe -c `"pacman-key --init`"".PadLeft($wid, $dash)
+bash.exe -c `"pacman-key --init`" 2> $null
+
+Write-Host " bash.exe -c `"pacman-key --populate msys2`"".PadLeft($wid, $dash)
+bash.exe -c `"pacman-key --populate msys2`" 2> $null
+
+Write-Host " pacman --noconfirm -Syyuu".PadLeft($wid, $dash)
+pacman.exe -Syyuu --noconfirm 2> $null
+
+# install msys2 packages
+Write-Host " Install msys2 packages".PadLeft($wid, $dash)
+pacman.exe -S --noconfirm --needed --noprogressbar base-devel compression
+
+# mingw package list
+$tools = "___clang ___cmake ___llvm  ___toolchain ___ragel"
+
+# install mingw64 packages
+Write-Host " Install mingw64 packages".PadLeft($wid, $dash)
+$pre = "mingw-w64-x86_64-"
+pacman.exe -S --noconfirm --needed --noprogressbar $tools.replace('___', $pre).split(' ')
+
+# install mingw32 packages
+Write-Host " Install mingw32 packages".PadLeft($wid, $dash)
+$pre = "mingw-w64-i686-"
+pacman.exe -S --noconfirm --needed --noprogressbar $tools.replace('___', $pre).split(' ')
+
+# clean all packages to decrease image size ?
+Write-Host " Clean packages".PadLeft($wid, $dash)
+pacman -Scc --noconfirm 
+
+Write-Host
+Write-Host " Installed mingw64 packages".PadLeft($wid, $dash)
+pacman.exe -Qs mingw-w64-x86_64- | grep local/ | sed -r "s/local\/| \(.+\)$//g"
+
+Write-Host
+Write-Host " Installed mingw32 packages".PadLeft($wid, $dash)
+pacman.exe -Qs mingw-w64-i686- | grep local/ | sed -r "s/local\/| \(.+\)$//g"
+
+Write-Host
+Write-Host " Installed msys2 packages".PadLeft($wid, $dash)
+pacman.exe -Qs | grep local/ | grep -v mingw-w64 | sed -r "s/local\/| \(.+\)$//g"