Fix build

Use more recent `gn`
Disable some functionality to broke the build (whether we should enable it back remains TBD)
Change Skia flags to fix up dependencies
Apply patch so missing Skia deps don't break Aseprite's build

Many of these changes were imported from my work on `aseprite-git`
https://github.com/ISSOtm/PKGBUILDs/tree/aseprite-git/aseprite-git

.gitignore

@@ -6,4 +6,5 @@
 !/is_clang.py
 !/shared-libarchive.patch
 !/shared-libwebp.patch
+!/shared-skia-deps.patch
 !/optional-pixman.patch