[KYUUBI #1804]Avoid nightly build for forked repos

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### _How was this patch tested?_
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Closes #1805 from link3280/improvement/KYUUBI-1804.

Closes #1804

4f423ee [Paul Lin] [KYUUBI #1804]Avoid nightly build for forked repos

Authored-by: Paul Lin <paullin3280@gmail.com>
Signed-off-by: Cheng Pan <chengpan@apache.org>

.github/workflows/nightly.yml

@@ -7,6 +7,7 @@ on:
 jobs:
   build:
     name: Build
+    if: ${{ startsWith(github.repository, 'apache/') }}
     runs-on: ubuntu-20.04
     strategy:
       matrix: