RFR: 8353573: System giflib not found by configure if it's not in system directories

[snake66]

The configure script is not able to pick up the giflib installed via system packages if it's not located in the system include and lib directories. Since giflib does not provide a pkgconfig, arguments to specify the location of the include and library files needs to be added to the configure script. 

This work is sponsored by The FreeBSD Foundation

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Commit messages:
 - 8353573: System giflib not found by configure if it's not in system directories

Changes: https://git.openjdk.org/jdk/pull/24404/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24404&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8353573
  Stats: 39 lines in 2 files changed: 35 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/24404.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24404/head:pull/24404

PR: https://git.openjdk.org/jdk/pull/24404