Fix building Flatpak in Ubuntu 22.04 in WSL2

- Use LF line ending for Linux scripts even on Windows
- Better handling of paths that include spaces
- Avoid new f-string syntax to support Python 3.10
- Replace shell substitution syntax that dash doesn't support

Author: Ortham

.gitattributes

@@ -1,5 +1,7 @@
 # Auto detect text files and perform LF normalization
 * text=auto
+*.sh text eol=lf
+/resources/linux/* text eol=lf
 
 # Custom for Visual Studio
 *.cs     diff=csharp

scripts/build_flatpak.sh

@@ -10,7 +10,7 @@ then
     BRANCH_NAME="$(git rev-parse --abbrev-ref HEAD)"
     DESCRIPTION="$(git describe --tags --long --abbrev=7)"
     PACKAGE_FILENAME="loot_${DESCRIPTION}_${BRANCH_NAME}.flatpak"
-    PACKAGE_FILENAME="${PACKAGE_FILENAME//[\/<>\"|]/_}"
+    PACKAGE_FILENAME="$(echo $PACKAGE_FILENAME | sed 's/[\/<>\"|]/_/g')"
 fi
 
 cd build