[riscv-port-jdk11u:riscv-port] RFR: 8328948: GHA: Restoring sysroot from cache skips the build after JDK-8326960 [v2]

[Fei Yang]

> Fixes a recent GHA regression. Applies cleanly.
> 
> - [x] GHA, first run passes cross-builds
> - [ ] GHA, second run passes cross-builds

Fei Yang has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:

 - Merge branch 'riscv-port' into 8328948-backport
 - backport

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Changes:
  - all: https://git.openjdk.org/riscv-port-jdk11u/pull/15/files
  - new: https://git.openjdk.org/riscv-port-jdk11u/pull/15/files/67683034..010f3c0c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=riscv-port-jdk11u&pr=15&range=01
 - incr: https://webrevs.openjdk.org/?repo=riscv-port-jdk11u&pr=15&range=00-01

  Stats: 2373 lines in 30 files changed: 629 ins; 1123 del; 621 mod
  Patch: https://git.openjdk.org/riscv-port-jdk11u/pull/15.diff
  Fetch: git fetch https://git.openjdk.org/riscv-port-jdk11u.git pull/15/head:pull/15

PR: https://git.openjdk.org/riscv-port-jdk11u/pull/15