dev-libs/libbpf: Fix install in prefix

Without this patch install would cause:

 * QA Notice: the following files are outside of the prefix:
 * /usr
[...]
 * /usr/include/bpf/uapi/linux/bpf.h
 * /usr/include/bpf/libbpf_legacy.h
 * ERROR: dev-libs/libbpf-1.0.1::gentoo failed:
 *   Aborting due to QA concerns: there are files installed outside the prefix

I replaced the declaration of LIBDIR because it is
default-initialized to:
  LIBDIR ?= $(PREFIX)/$(LIBSUBDIR)
across all versions of libbpf versions with ebuild.

Signed-off-by: YiFei Zhu <zhuyifei@google.com>
Closes: https://github.com/gentoo/gentoo/pull/28323
Signed-off-by: Sam James <sam@gentoo.org>

dev-libs/libbpf/libbpf-0.8.1.ebuild

@@ -34,7 +34,9 @@ PATCHES=(
 src_configure() {
 	append-cflags -fPIC
 	tc-export CC AR
-	export LIBSUBDIR="$(get_libdir)" V=1
+	export LIBSUBDIR="$(get_libdir)"
+	export PREFIX="${EPREFIX}/usr"
+	export V=1
 }
 
 src_install() {

dev-libs/libbpf/libbpf-1.0.0-r1.ebuild

@@ -34,7 +34,7 @@ src_configure() {
 	append-cflags -fPIC
 	tc-export CC AR
 	export LIBSUBDIR="$(get_libdir)"
-	export LIBDIR="${EPREFIX}/usr/$(get_libdir)"
+	export PREFIX="${EPREFIX}/usr"
 	export V=1
 }
 

dev-libs/libbpf/libbpf-1.0.1.ebuild

@@ -34,7 +34,7 @@ src_configure() {
 	append-cflags -fPIC
 	tc-export CC AR
 	export LIBSUBDIR="$(get_libdir)"
-	export LIBDIR="${EPREFIX}/usr/$(get_libdir)"
+	export PREFIX="${EPREFIX}/usr"
 	export V=1
 }
 

dev-libs/libbpf/libbpf-9999.ebuild

@@ -34,7 +34,7 @@ src_configure() {
 	append-cflags -fPIC
 	tc-export CC AR
 	export LIBSUBDIR="$(get_libdir)"
-	export LIBDIR="${EPREFIX}/usr/$(get_libdir)"
+	export PREFIX="${EPREFIX}/usr"
 	export V=1
 }