[fuchsia] Update local-sdk script for fx set command.

Change-Id: I1ca0b592a9620d85e204302b6f0ce53cf915b588
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1573095
Auto-Submit: Fabrice de Gans-Riberi <fdegans@chromium.org>
Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Commit-Queue: Fabrice de Gans-Riberi <fdegans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#652216}

tools/fuchsia/local-sdk.py

@@ -33,11 +33,9 @@ def EnsureEmptyDir(path):
 
 def BuildForArch(arch):
   build_dir = 'out/release-' + arch
-  Run('scripts/fx', 'set', 'sdk_image.' + arch,
-      '--with=//topaz/packages/sdk:topaz',
-      '--args=is_debug=false', '--args=build_sdk_archives=true',
-      '--build-dir=' + build_dir)
-  Run('scripts/fx', 'build-zircon')
+  Run('scripts/fx', '--dir', build_dir, 'set', 'sdk_image.' + arch,
+      '--with=//topaz/packages/sdk:topaz', '--args=is_debug=false',
+      '--args=build_sdk_archives=true')
   Run('scripts/fx', 'build', 'topaz/public/sdk:topaz')