Switch the sfx installer to zstandard

Using a 7zip fork with zstandard support: https://github.com/mcmilk/7-Zip-zstd

Saves 20% CPU when extracting, also uses ~50MB less peak memory.
Downside is a 5% larger installer.

.gitignore

@@ -0,0 +1,3 @@
+_cache
+*.exe
+*.xz

create-sfx.sh

@@ -0,0 +1,28 @@
+#!/bin/bash
+# usage: ./create-sfx.sh /some/path/to/msys64 installer.exe
+
+set -e
+
+# Download and extract https://github.com/mcmilk/7-Zip-zstd
+NAME="7z21.03-zstd-x64"
+CHECKSUM="531b20dfb03d8f30f61ae56a181610bbb6f3cf7cc71dac1d8f95511289de76f3"
+DIR="$( cd "$( dirname "$0" )" && pwd )"
+mkdir -p "$DIR/_cache"
+BASE="$DIR/_cache/$NAME"
+if [ ! -f "$BASE.exe" ]; then
+    curl --fail -L "https://github.com/mcmilk/7-Zip-zstd/releases/download/v21.03-v1.5.0-R2/$NAME.exe" -o "$BASE.exe"
+fi
+echo "$CHECKSUM $BASE.exe" | sha256sum --quiet --check
+if [ ! -d "$BASE" ]; then
+    7z e -o"$BASE" "$DIR/_cache/$NAME.exe"
+fi
+
+# Creat SFX installer
+INPUT="$1"
+OUTPUT="$2"
+TEMP="$OUTPUT.payload"
+
+rm -f "$TEMP"
+"$BASE/7z" a "$TEMP" -ms1T -m0=zstd -mx22 "$INPUT"
+cat "$BASE/7zCon.sfx" "$TEMP" > "$OUTPUT"
+rm "$TEMP"

fetch-sfx.sh

@@ -1,10 +0,0 @@
-#!/bin/bash
-
-set -e
-
-# Fetch 7zCon.sfx from upstream 7-zip
-curl "https://www.7-zip.org/a/7z1900.exe" -o 7z1900.exe
-echo "759aa04d5b03ebeee13ba01df554e8c962ca339c74f56627c8bed6984bb7ef80 7z1900.exe" | sha256sum --check
-7z x -o7zout 7z1900.exe
-cp 7zout/7zCon.sfx .
-rm -Rf 7zout 7z1900.exe

make-msys2-installer

@@ -85,9 +85,7 @@ create_archives() {
     fi
 
     # self extracting cli 7z archive
-    7z a -mx=9  "${_thisdir}/_temp.7z" "msys${_bitness}"
-    cat ${_thisdir}/7zCon.sfx "${_thisdir}/_temp.7z" > "${_thisdir}/${_filename3}"
-    rm "${_thisdir}/_temp.7z"
+    "${_thisdir}/create-sfx.sh" "msys${_bitness}" "${_thisdir}/${_filename3}"
   popd > /dev/null
 }