[gif-load]: add new port

[Saikari (luadebug)]

• Changes comply with the maintainer guide.
• The packaged project is mature and ready for broad sharing with vcpkg users
  • Has a release at least 6 months old or 6 months of demonstrated public development
  • Is an official component of something else meeting that criteria
  • Some other reason (please explain)
• The packaged project shows strong association with the chosen port name. Check this box if at least one of the following criteria is met:
  • The project is in Repology: https://repology.org/project//versions
  • The project is amongst the first web search results for "" or " C++". Include a screenshot of the search engine results in the PR.
  • The port name follows the 'GitHubOrg-GitHubRepo' form or equivalent Owner-Project form.
• Optional dependencies of the build are all controlled by the port. A dependency is controlled if it is declared an unconditional dependency in vcpkg.json, or explicitly disabled through patches or build system arguments such as CMAKE_DISABLE_FIND_PACKAGE_Xxx or VCPKG_LOCK_FIND_PACKAGE
• The versioning scheme in vcpkg.json matches what upstream says.
• The license declaration in vcpkg.json matches what upstream says.
• The installed as the "copyright" file matches what upstream says.
• The source code of the component installed comes from an authoritative source.
• The generated "usage text" is brief and accurate. See adding-usage for context. Don't add a usage file if the automatically generated usage is correct.
• The version database is fixed by rerunning ./vcpkg x-add-version --all and committing the result.
• Exactly one version is added in each modified versions file.

[Billy O'Neal (BillyONeal)]

Also submitted as luadebug#3

Thanks!

[Billy O'Neal (BillyONeal)]

Suggested change

	file(WRITE "${SOURCE_PATH}/UNLICENSE" [[This is free and unencumbered software released into the public domain.
	Anyone is free to copy, modify, publish, use, compile, sell, or
	distribute this software, either in source code form or as a compiled
	binary, for any purpose, commercial or non-commercial, and by any means.
	In jurisdictions that recognize copyright laws, the author or authors
	of this software dedicate any and all copyright interest in the
	software to the public domain. We make this dedication for the benefit
	of the public at large and to the detriment of our heirs and
	successors. We intend this dedication to be an overt act of
	relinquishment in perpetuity of all present and future rights to this
	software under copyright law.
	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
	EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
	MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
	IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
	OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
	ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
	OTHER DEALINGS IN THE SOFTWARE.
	]])
	vcpkg_install_copyright(FILE_LIST "${SOURCE_PATH}/UNLICENSE")
	vcpkg_install_copyright(FILE_LIST "${SOURCE_PATH}/gif_load.h")

Ditto #53208 (comment)

[Billy O'Neal (BillyONeal)]

Note that this isn't actually running the result; it's a compile only test, so I'm not sure how plausible this needs to be.

[Billy O'Neal (BillyONeal)]

Thanks!