[version] add __variant__

Specifies origin and OS of executable files.
For example 'stable/windows'.

scripts/release.sh

@@ -53,19 +53,20 @@ build-linux() {
     cd "${ROOTDIR}"
     echo Building Linux executable
 
-    build-vm 'ubuntu22.04' 'gallery-dl.bin'
+    build-vm 'ubuntu22.04' 'gallery-dl.bin' 'linux'
 }
 
 build-windows() {
     cd "${ROOTDIR}"
     echo Building Windows executable
 
-    build-vm 'windows7_x86_sp1' 'gallery-dl.exe'
+    build-vm 'windows7_x86_sp1' 'gallery-dl.exe' 'windows'
 }
 
 build-vm() {
     VMNAME="$1"
     BINNAME="$2"
+    LABEL="$3"
     TMPPATH="/tmp/gallery-dl/dist/$BINNAME"
 
     # launch VM
@@ -77,6 +78,11 @@ build-vm() {
     cp -a -t /tmp/gallery-dl -- \
         ./gallery_dl ./scripts ./data ./setup.py ./README.rst
 
+    # update __variant__
+    sed -i \
+        -e "s#\(__variant__ *=\).*#\1 \"stable/${LABEL}\"#" \
+        /tmp/gallery-dl/gallery_dl/version.py
+
     # remove old executable
     rm -f "./dist/$BINNAME"