fix: Set gzip to default compression format

Turns out rpm-ostree doesn't quite support the new compression format yet.

src/commands/build.rs

@@ -47,7 +47,7 @@ pub struct BuildCommand {
 
     /// The compression format the images
     /// will be pushed in.
-    #[arg(short, long, default_value_t = CompressionType::Zstd)]
+    #[arg(short, long, default_value_t = CompressionType::Gzip)]
     #[builder(default)]
     compression_format: CompressionType,
 

src/drivers/opts/build.rs

@@ -6,8 +6,8 @@ use typed_builder::TypedBuilder;
 #[derive(Debug, Copy, Clone, Default, ValueEnum)]
 pub enum CompressionType {
     #[default]
-    Zstd,
     Gzip,
+    Zstd,
 }
 
 impl std::fmt::Display for CompressionType {