RFR: Jextract build fails on Windows (take two)

[Maurizio Cimadamore]

It seems like [1] did not address all the issues with Windows build.
This patch makes the quoting of the jlink options explicit, and different between Windows and the other systems.

I've verified on Windows (using powershell) and Ubuntu 20.04. Seems to work ok.

[1] - https://github.com/openjdk/jextract/pull/24

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Commit messages:
 - Initial push
 - README.md change for additional clang options (review suggestion)
 - argValue check for starting with '-' was in wrong place.
 - added test for -D option.
 - 7903164: cleanup jextract options

Changes: https://git.openjdk.java.net/jextract/pull/24/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jextract&pr=24&range=00
  Stats: 212 lines in 50 files changed: 124 ins; 9 del; 79 mod
  Patch: https://git.openjdk.java.net/jextract/pull/24.diff
  Fetch: git fetch https://git.openjdk.java.net/jextract pull/24/head:pull/24

PR: https://git.openjdk.java.net/jextract/pull/24