Added own hacky mangohud ebuilds

I cloned the upstream repo myself to pull the meson subprojects, and
tarballed them. They are then extracted in src_prepare() to the right
right directory to build mangohud successfully.

This was to fix new vulkan headers breaking mangohud, so the subprojects
are used instead.

games-util/mangohud/Manifest

@@ -0,0 +1 @@
+DIST mangohud-0.6.9.1.tar.gz 14853039 BLAKE2B e34674dc6877249bdfa8929fec1b337876f6d69c42e5c35c37813adca67232084178247d8bef1bf9c0471f9966474df27b25564644dea55e90b3b3c6b9fbf4d1 SHA512 540fb4d1c5494e1305553600f76c57ba75c465df4b76ddbe1f15c418fa9a7e26c66be7ce64a13bfd7c5073bcb985cd28b2876252cdff7c43793d22a40eb78a87

games-util/mangohud/files/mangohud-0.6.6-meson-fix-imgui-dep.patch

@@ -0,0 +1,14 @@
+# We provide media-libs/imgui in guru
+
+--- a/meson.build
++++ b/meson.build
+@@ -251,8 +251,7 @@ elif sizeof_ptr == 4
+   pre_args += '-DMANGOHUD_ARCH="32bit"'
+ endif
+
+-dearimgui_sp = subproject('imgui', default_options: imgui_options)
+-dearimgui_dep = dearimgui_sp.get_variable('imgui_dep')
++dearimgui_dep = dependency('imgui')
+
+ spdlog_dep = cpp.find_library('spdlog', required: get_option('use_system_spdlog'))
+ if not spdlog_dep.found()

games-util/mangohud/mangohud-0.6.9.1.ebuild

@@ -0,0 +1,106 @@
+# Copyright 1999-2022 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+PYTHON_COMPAT=( python3_{10..11} )
+
+inherit python-any-r1 meson
+
+MY_PV=$(ver_cut 1-3)
+[[ -n "$(ver_cut 4)" ]] && MY_PV_REV="-$(ver_cut 4)"
+
+DESCRIPTION="Vulkan and OpenGL overlay for monitoring FPS, sensors, system load and more"
+HOMEPAGE="https://github.com/flightlessmango/MangoHud"
+
+if [[ ${PV} == 9999 ]]; then
+	inherit git-r3
+	EGIT_REPO_URI="https://github.com/flightlessmango/MangoHud.git"
+else
+	SRC_URI="https://github.com/flightlessmango/MangoHud/archive/v${MY_PV}${MY_PV_REV}.tar.gz -> ${P}.tar.gz"
+	KEYWORDS="~amd64"
+fi
+
+LICENSE="MIT"
+SLOT="0"
+IUSE="+dbus debug +X xnvctrl wayland video_cards_nvidia"
+
+REQUIRED_USE="
+	|| ( X wayland )
+	xnvctrl? ( video_cards_nvidia )"
+
+BDEPEND="
+	app-arch/unzip
+	$(python_gen_any_dep 'dev-python/mako[${PYTHON_USEDEP}]')
+"
+
+python_check_deps() {
+	python_has_version "dev-python/mako[${PYTHON_USEDEP}]"
+}
+
+DEPEND="
+	~media-libs/imgui-1.81[opengl,vulkan]
+	dev-libs/spdlog
+	dev-util/glslang
+	>=dev-util/vulkan-headers-1.2
+	media-libs/vulkan-loader
+	media-libs/libglvnd
+	x11-libs/libdrm
+	dbus? ( sys-apps/dbus )
+	X? ( x11-libs/libX11 )
+	video_cards_nvidia? (
+		x11-drivers/nvidia-drivers
+		xnvctrl? ( x11-drivers/nvidia-drivers[static-libs] )
+	)
+	wayland? ( dev-libs/wayland )
+"
+
+RDEPEND="${DEPEND}"
+
+[[ "$PV" != "9999" ]] && S="${WORKDIR}/MangoHud-${PV}"
+
+PATCHES=(
+	"${FILESDIR}/mangohud-0.6.6-meson-fix-imgui-dep.patch"
+)
+
+src_unpack() {
+	default
+	[[ $PV == 9999 ]] && git-r3_src_unpack
+	[[ $PV != 9999 && -n "${MY_PV_REV}" ]] && ( mv "${WORKDIR}/MangoHud-${MY_PV}${MY_PV_REV}" "${WORKDIR}/MangoHud-${PV}" || die )
+}
+
+src_prepare() {
+	default
+	# replace all occurences of "#include <imgui.h>" to "#include <imgui/imgui.h>"
+	find . -type f -exec sed -i 's/#include <imgui.h>/#include <imgui\/imgui.h>/g' {} \;
+	find . -type f -exec sed -i 's/#include "imgui.h"/#include <imgui\/imgui.h>/g' {} \;
+	# extract meson pre-generated subproject as a hacky way to bypass not being
+	# able to download meson subprojects at runtime
+	tar -xf "${FILESDIR}/meson-subproject_Vulkan-Headers-1.2.158.tar.gz" -C "${WORKDIR}/MangoHud-${PV}/subprojects"
+	tar -xf "${FILESDIR}/meson-subproject_nlohmann_json-3.10.5.tar.gz" -C "${WORKDIR}/MangoHud-${PV}/subprojects"
+}
+
+src_configure() {
+	local emesonargs=(
+		-Dappend_libdir_mangohud=false
+		-Duse_system_spdlog=enabled
+		-Dinclude_doc=false
+		$(meson_feature video_cards_nvidia with_nvml)
+		$(meson_feature xnvctrl with_xnvctrl)
+		$(meson_feature X with_x11)
+		$(meson_feature wayland with_wayland)
+		$(meson_feature dbus with_dbus)
+	)
+	meson_src_configure
+}
+
+pkg_postinst() {
+	if ! use xnvctrl; then
+		einfo ""
+		einfo "If mangohud can't get GPU load, or other GPU information,"
+		einfo "and you have an older Nvidia device."
+		einfo ""
+		einfo "Try enabling the 'xnvctrl' useflag."
+		einfo ""
+	fi
+}