dnf: enable fastestmirror by default

Enabling the fastestmirror plugin allows dnf to choose the fastest
(also usually the closest) mirror to the instance of osbuild. It
has no effect on builds that force the use of a specific server
or mirror.

Signed-off-by: Major Hayden <major@redhat.com>

stages/org.osbuild.dnf

@@ -22,6 +22,7 @@ arguments generated from the stage options:
 * `--forcearch {basearch}`
 * `--releasever {releasever}`
 * `--setopt install_weak_deps={install_weak_deps}`
+* `--setopt fastestmirror={fastestmirror}`
 * `--config /tmp/dnf.conf`
 * `--exclude {pkg}` for each item in `exclude_packages`
 
@@ -123,6 +124,11 @@ STAGE_OPTS = """
     "type": "boolean",
     "default": true
   },
+  "fastestmirror": {
+    "description": "Whether DNF should choose the fastest mirror available",
+    "type": "boolean",
+    "default": true
+  },
   "exclude_packages": {
     "description": "List of package-specs to --exclude",
     "type": "array",
@@ -210,6 +216,7 @@ def main(tree, options):
     basearch = options["basearch"]
     operation = options.get("operation", "install")
     weak_deps = options.get("install_weak_deps", True)
+    fastestmirror = options.get("fastestmirror", True)
     exclude_packages = options.get("exclude_packages", [])
     module_platform_id = options.get("module_platform_id", None)
 
@@ -253,6 +260,7 @@ def main(tree, options):
             "--forcearch", basearch,
             "--setopt", "reposdir=",
             "--setopt", f"install_weak_deps={weak_deps}",
+            "--setopt", f"fastestmirror={fastestmirror}",
             "--setopt", f"skip_if_unavailable=false",
             "--releasever", releasever,
             "--noplugins",