[foreign-jextract] Integrated: * Fixed include path to be OS/SDK version independent

[Athijegannathan Sundararajan]

* Fixed CSupport.* and Cstring.* clash in GitClone.java

all samples run fine on Mac OS 10.5.5

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Commit messages:
 - * Fixed include path to be OS/SDK version independent

Changes: https://git.openjdk.java.net/panama-foreign/pull/210/files
 Webrev: https://webrevs.openjdk.java.net/panama-foreign/210/webrev.00
  Stats: 51 lines in 2 files changed: 2 ins; 2 del; 47 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/210.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/210/head:pull/210

PR: https://git.openjdk.java.net/panama-foreign/pull/210