[foreign-memaccess+abi] RFR: 8264280: Foreign linker should be more friendly with implicit scopes (followup)

[Maurizio Cimadamore]

The newly added test sometimes fails spuriously. This is caused by the fact that the library is loaded to an address that is a multiple of the expected layout constraints.
The fix is to make the test tolerant to this situation - and check that, if no exception is thrown, the symbol alignment must be the same as the one specified by the layout.

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Commit messages:
 - Make test more robust

Changes: https://git.openjdk.java.net/panama-foreign/pull/484/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=484&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8264280
  Stats: 13 lines in 1 file changed: 10 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/484.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/484/head:pull/484

PR: https://git.openjdk.java.net/panama-foreign/pull/484