RFR: 8273494: Zero: Put libjvm.so into "zero" folder, not "server"

[Aleksey Shipilev]

Currently, the build system defaults the libjvm.so location to "server".  This makes looking for `libjvm.so` awkward, see JDK-8273487 for example. We need to see if moving the libjvm.so to a proper location breaks anything. 

Additional testing:
 - [x] Linux x86_64 Zero build
 - [x] Linux x86_64 Zero bootcycle-images
 - [ ] Linux x86_64 Zero `tier1`

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Commit messages:
 - Fix

Changes: https://git.openjdk.java.net/jdk/pull/5440/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5440&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8273494
  Stats: 14 lines in 6 files changed: 0 ins; 3 del; 11 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5440.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5440/head:pull/5440

PR: https://git.openjdk.java.net/jdk/pull/5440