games-emulation/dolphin: use bundled vulkan-headers

Gentoo's dev-util/vulkan-headers removed API that dolphin relied on.
Let's sue bundled headers. Fix is proposed by Gabriel Marcano.

Reported-by: Gabriel Marcano
Closes: https://bugs.gentoo.org/729832
Package-Manager: Portage-2.3.103, Repoman-2.3.23
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>

games-emulation/dolphin/dolphin-9999.ebuild

@@ -61,7 +61,6 @@ RDEPEND="
 "
 DEPEND="${RDEPEND}
 	app-arch/zip
-	dev-util/vulkan-headers
 	media-libs/freetype
 	sys-devel/gettext
 	virtual/pkgconfig"
@@ -79,6 +78,12 @@ src_prepare() {
 	local KEEP_SOURCES=(
 		Bochs_disasm
 		FreeSurround
+
+		# vulkan's API is not backwards-compatible:
+		# new release dropped VK_PRESENT_MODE_RANGE_SIZE_KHR
+		# but dolphin still relies on it, bug #729832
+		Vulkan
+
 		cpp-optparse
 		# no support for for using system library
 		glslang