[jdk21u-dev] RFR: 8326960: GHA: RISC-V sysroot cannot be debootstrapped due to ongoing Debian t64 transition

[Aleksey Shipilev]

Makes GHA cross-compilation jobs clean again.

Additional testing: 
- [ ] GHA

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Commit messages:
 - Backport f207aa94f9296932276c2952252b263efc793b3f

Changes: https://git.openjdk.org/jdk21u-dev/pull/394/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=394&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8326960
  Stats: 15 lines in 1 file changed: 14 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/394.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/394/head:pull/394

PR: https://git.openjdk.org/jdk21u-dev/pull/394