[jdk11u-dev] RFR: 8329348: jdk11u build for Windows AArch64 fails

[Saint Wesonga]

The root cause of the build error 'No rule to make target .../windows/conf/tzmappings' when building jdk11u for Windows AArch64 is that the GENSRC_TARGETS have not been built. This happens because the buildjdk is x86 but the target jdk is aarch64. Reusing artifacts is not correct in this scenario. The fix is to ensure that the required targets are built unconditionally for Windows AArch64.

Note that the existing checks for CREATING_BUILDJDK were also found to be incorrect in https://bugs.openjdk.org/browse/JDK-8217739

Builds on macOS, Linux, and Windows across both x64/AArch64 succeeded with this fix.

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Commit messages:
 - Fix 'No rule to make target .../windows/conf/tzmappings' error

Changes: https://git.openjdk.org/jdk11u-dev/pull/2668/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2668&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8329348
  Stats: 12 lines in 1 file changed: 11 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2668.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2668/head:pull/2668

PR: https://git.openjdk.org/jdk11u-dev/pull/2668