stages/org.osbuild.qemu: make qcow2 compression optional

Modify the stages/org.osbuild.qemu stage such that compression is.
Optional. This resolves the image size differences between an image
built with coreos assember vs osbuild, as discussed in:
coreos/fedora-coreos-tracker#1653 (comment)

stages/org.osbuild.qemu

@@ -24,13 +24,19 @@ SCHEMA_2 = r"""
     "description": "Create a qcow2 image",
     "type": "object",
     "required": ["type"],
+    "not": {"required": ["disable-compression", "compat"]},
     "additionalProperties": false,
     "properties": {
       "type": {
         "description": "The type of the format, here 'qcow2'",
         "type": "string",
         "enum": ["qcow2"]
       },
+      "disable-compression": {
+        "description": "Disable compression of the qcow2 image",
+        "type": "boolean",
+        "enum": [true]
+      },
       "compat": {
         "description": "The qcow2-compatibility-version to use",
         "type": "string"
@@ -140,9 +146,13 @@ SCHEMA_2 = r"""
 
 
 def qcow2_arguments(options):
-    argv = ["-c"]
+    argv = []
+    disable_compression = options.get("disable-compression", False)
     compat = options.get("compat")
 
+    if not disable_compression:
+      argv += ["-c"]
+
     if compat:
         argv += ["-o", f"compat={compat}"]
     return argv

test/data/manifests/fedora-coreos-container.mpp.yaml

@@ -611,4 +611,4 @@ pipelines:
           filename: qemu.qcow2
           format:
             type: qcow2
-            compat: '1.1'
+            disable-compression: true