buck2/github: replace --out-dir with --artifact-dir

Summary: It was renamed long time ago: rust-lang/cargo#6790

Differential Revision: D66011214

Author: KapJI

.github/actions/build_debug/action.yml

@@ -6,5 +6,5 @@ runs:
   - name: Build buck2 binary (debug)
     run: |-
       mkdir $RUNNER_TEMP/artifacts
-      cargo build --bin=buck2 -Z unstable-options --out-dir=$RUNNER_TEMP/artifacts
+      cargo build --bin=buck2 -Z unstable-options --artifact-dir=$RUNNER_TEMP/artifacts
     shell: bash

.github/actions/build_release/action.yml

@@ -6,5 +6,5 @@ runs:
   - name: Build buck2 binary (release)
     run: |-
       mkdir $RUNNER_TEMP/artifacts
-      cargo build --bin=buck2 --release -Z unstable-options --out-dir=$RUNNER_TEMP/artifacts
+      cargo build --bin=buck2 --release -Z unstable-options --artifact-dir=$RUNNER_TEMP/artifacts
     shell: bash