RFR: 7903200: sync makefiles to build jmod for jextract

[Athijegannathan Sundararajan]

Fixing makefiles for jmod creation. Changed the name of the jmod file.

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Commit messages:
 - 7903200: sync makefiles to build jmod for jextract

Changes: https://git.openjdk.java.net/jextract/pull/38/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jextract&pr=38&range=00
  Issue: https://bugs.openjdk.java.net/browse/CODETOOLS-7903200
  Stats: 31 lines in 2 files changed: 15 ins; 10 del; 6 mod
  Patch: https://git.openjdk.java.net/jextract/pull/38.diff
  Fetch: git fetch https://git.openjdk.java.net/jextract pull/38/head:pull/38

PR: https://git.openjdk.java.net/jextract/pull/38