Rebase to webkitgtk 2.54.0 (WebKitGTK Security Advisory WSA-2026-0006),
aligning with the release RHEL 9 ships (webkit2gtk3-2.54.0-1.el9_8,
RHSA-2026:69098).
Adopt the CentOS Stream 9 2.54.0 packaging patch set; skia-s390x.patch
and mimalloc.patch are new there for 2.54.0, fix-eclipse.patch is from
c9s 2.54.0-2 and reverts 317619@main, which aborts Eclipse/SWT
applications on a RELEASE_ASSERT in initializeMainThread.
Drop fix-renderflexbox-typename.patch (was Patch17); the code it patched is
gone on 2.54.0.
Build with gcc-toolset-14 (GCC 14) instead of gcc-toolset-12; GCC 12
cannot compile 2.54.0 (ANGLE ResourceMap static_assert, LayoutRect
constexpr).
Backport the GStreamerCommon.h <WebCore/GraphicsTypesGL.h> include from
upstream 2.54.1; GCC resolves the symlinked WebCore private headers to
their real path, so the quoted include is not found when building the PCH.
Drop the vendored Skia backports for CVE-2026-5870, CVE-2026-7920,
CVE-2026-7923, CVE-2026-10009 and CVE-2026-11663 (was Patch20..Patch24);
the Skia snapshot bundled with 2.54.0 already includes them.