RFR: 7903591: Do not re-run cmake tasks if inputs didn't change

[Jorn Vernee]

Defines inputs and outputs for the cmake* tasks, to avoid re-running them every time.

I also noticed that the CMakeLists.txt still uses a glob corresponding to the old test directory structure. It will essentially look for `*lib*.c` files from the project root. I've fixed this to only look in the `test` sub directory.

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Commit messages:
 - Track inputs and outputs for cmake tasks

Changes: https://git.openjdk.org/jextract/pull/142/files
 Webrev: https://webrevs.openjdk.org/?repo=jextract&pr=142&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903591
  Stats: 12 lines in 2 files changed: 9 ins; 2 del; 1 mod
  Patch: https://git.openjdk.org/jextract/pull/142.diff
  Fetch: git fetch https://git.openjdk.org/jextract.git pull/142/head:pull/142

PR: https://git.openjdk.org/jextract/pull/142