RFR: fixing jextract sample issues for jdk 22 [v2]

[Athijegannathan Sundararajan]

> * re-generated libjimage sources and manually adopted for library loding.
> * avoid attempting to generate unsupported type constants ("long double")
> * adjust shell scripts for different versions of native libraries
> * allow Python home to be overridden by env. vars

Athijegannathan Sundararajan has updated the pull request incrementally with one additional commit since the last revision:

  adjusted compilesource.sh scripts to generate sources under "src" different
  from the directory where .class files are created.

-------------

Changes:
  - all: https://git.openjdk.org/jextract/pull/174/files
  - new: https://git.openjdk.org/jextract/pull/174/files/ffd9e0f2..2f2db031

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jextract&pr=174&range=01
 - incr: https://webrevs.openjdk.org/?repo=jextract&pr=174&range=00-01

  Stats: 63 lines in 19 files changed: 24 ins; 0 del; 39 mod
  Patch: https://git.openjdk.org/jextract/pull/174.diff
  Fetch: git fetch https://git.openjdk.org/jextract.git pull/174/head:pull/174

PR: https://git.openjdk.org/jextract/pull/174