Use optional asset archive instead of file

appveyor.yml

@@ -37,7 +37,7 @@ environment:
  ASSET_ARCHIVE_PATCH_PATH: https://github.com/mazmazz/SRB2/releases/download/SRB2_assets/SRB2-v2122-patch-assets.7z
  ASSET_ARCHIVE_X86_PATH: https://github.com/mazmazz/SRB2/releases/download/SRB2_assets/SRB2-v2122-x86-assets.7z
  ASSET_ARCHIVE_X64_PATH: https://github.com/mazmazz/SRB2/releases/download/SRB2_assets/SRB2-v2122-x64-assets.7z
- ASSET_FILES_OPTIONAL_PATH: https://github.com/mazmazz/SRB2/releases/download/SRB2_assets/music.dta
+ ASSET_ARCHIVE_OPTIONAL_PATH: https://github.com/mazmazz/SRB2/releases/download/SRB2_assets/SRB2-v2122-optional-assets.7z
  # This is overridden to 1 for release tag builds
  ASSET_FILES_OPTIONAL_GET: 0
  # For patches, also include the X86/X64 DLLs.

deployer/appveyor/deployer.bat

@@ -102,10 +102,10 @@ if [%X86_64%] == [1] (
 )
 
 if [%ASSET_FILES_OPTIONAL_GET%] == [1] (
-    set "archivepath=%ASSET_FILES_OPTIONAL_PATH%"
+    set "archivepath=%ASSET_ARCHIVE_OPTIONAL_PATH%"
     call :ARCHIVE_NAME_PARTS
-    set "ASSET_FILES_OPTIONAL_PATH_LOCAL=!localarchivepath!"
-    if not exist "!localarchivepath!" appveyor DownloadFile "%ASSET_FILES_OPTIONAL_PATH%" -FileName "!localarchivepath!"
+    set "ASSET_ARCHIVE_OPTIONAL_PATH_LOCAL=!localarchivepath!"
+    if not exist "!localarchivepath!" appveyor DownloadFile "%ASSET_ARCHIVE_OPTIONAL_PATH%" -FileName "!localarchivepath!"
 )
 
 ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
@@ -120,7 +120,7 @@ mkdir "assets\deployer\patch"
 
 : Copy optional files to full installer (music.dta)
 if [%ASSET_FILES_OPTIONAL_GET%] == [1] (
-    xcopy /I /Y "%ASSET_FILES_OPTIONAL_PATH_LOCAL%" "assets\deployer\installer"
+    7z x -y "%ASSET_ARCHIVE_OPTIONAL_PATH_LOCAL%" -o"assets\deployer\installer" >null
 )
 
 : Copy EXE -- BUILD_PATH is from appveyor.yml