media-libs/openal: fix hardcoded paths in alconfig for Prefix

Closes: https://bugs.gentoo.org/883407
Signed-off-by: Fabian Groffen <grobian@gentoo.org>

media-libs/openal/openal-1.24.3.ebuild

@@ -6,7 +6,7 @@ EAPI=8
 # False positives because of REQUIRE vs BACKEND options() (conditionally set)
 # See bug #809314
 CMAKE_WARN_UNUSED_CLI=no
-inherit cmake-multilib
+inherit cmake-multilib prefix
 
 MY_P="${PN}-soft-${PV}"
 
@@ -53,6 +53,12 @@ PATCHES=(
 	"${FILESDIR}/${PN}-1.24.3-libfmt-libcxx-21.patch"
 )
 
+src_prepare() {
+	default
+	# bug #883407
+	hprefixify alc/alconfig.cpp || die
+}
+
 multilib_src_configure() {
 	local mycmakeargs=(
 		# See bug #809314 for getting both options for backends