media-libs/svt-vp9: add 0.3.1

For
```
 * QA Notice: Compatibility with CMake < 3.5 has been removed from CMake 4
```

See-also: https://github.com/OpenVisualCloud/SVT-VP9/issues/181
Closes: https://bugs.gentoo.org/901289
Signed-off-by: zyxhere💭 <zyx@envs.net>

media-libs/svt-vp9/Manifest

@@ -1 +1,2 @@
 DIST svt-vp9-0.3.0.gh.tar.gz 1009838 BLAKE2B 52cb9a4f500b3f5359655f55734bcec406034f6f24827587f00a37bd78640162aaba6939305d6b54945a6d9d967b78653b3a3c90a09942d09a0c55ce2b663657 SHA512 2b65d4cc731061c2a07010314f7c306664fd9cf122917f96b94ec87350c8bab1a1118527263eb39347a6f6f572088337e1c5f7ae738b52de30a28ccb54c321c1
+DIST svt-vp9-0.3.1.tar.gz 989489 BLAKE2B 626285ceeac7464d6cc3a8a80af50d7a9d38066ff3a74ad5f8c769c83e453b89df2b785f73242261fd1549332b25aa7213b73394e086aae153b7577696da19ce SHA512 98a36a154d0c62ed608f0f9a725d09aae6d679e6b310f81ebe3b02fd38db8e1a4843c6c8aac95ec75af94ecfc0599fc26a20e277028633170fb16dd4095db26d

media-libs/svt-vp9/svt-vp9-0.3.1.ebuild

@@ -0,0 +1,44 @@
+# Copyright 2026 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+inherit cmake
+
+DESCRIPTION="Scalable Video Technology for VP9 (SVT-VP9 Encoder)"
+HOMEPAGE="https://github.com/OpenVisualCloud/SVT-VP9"
+
+if [ ${PV} = "9999" ]; then
+	inherit git-r3
+	EGIT_REPO_URI="https://github.com/OpenVisualCloud/SVT-VP9.git"
+else
+	SRC_URI="
+		https://github.com/OpenVisualCloud/SVT-VP9/archive/v${PV}.tar.gz
+			-> ${P}.tar.gz
+	"
+
+	KEYWORDS="~amd64 ~arm64"
+	S="${WORKDIR}/SVT-VP9-${PV}"
+fi
+
+LICENSE="BSD-2-with-patent"
+SLOT="0/1"
+
+BDEPEND="dev-lang/nasm"
+
+src_prepare() {
+	# https://bugs.gentoo.org/901289
+	sed -i \
+	's/\(-fPIE\|-fPIC\|-D_FORTIFY_SOURCE=2\|-fstack-protector-strong\)\s*//g' \
+		CMakeLists.txt || die
+
+	cmake_src_prepare
+}
+
+src_configure() {
+	local mycmakeargs=(
+		-DBUILD_SHARED_LIBS=ON
+		)
+
+	cmake_src_configure
+}