libopus: fix pkg-config path

pkgs/development/libraries/libopus/default.nix

@@ -19,6 +19,7 @@ stdenv.mkDerivation rec {
   };
 
   patches = [
+    ./fix-pkg-config-paths.patch
     # Fix meson build for arm64. Remove with next release
     # https://gitlab.xiph.org/xiph/opus/-/merge_requests/59
     (fetchpatch {

pkgs/development/libraries/libopus/fix-pkg-config-paths.patch

@@ -0,0 +1,13 @@
+--- i/meson.build
++++ w/meson.build
+@@ -591,8 +591,8 @@ pkgconf = configuration_data()
+ 
+ pkgconf.set('prefix', join_paths(get_option('prefix')))
+ pkgconf.set('exec_prefix', '${prefix}')
+-pkgconf.set('libdir', '${prefix}/@0@'.format(get_option('libdir')))
+-pkgconf.set('includedir', '${prefix}/@0@'.format(get_option('includedir')))
++pkgconf.set('libdir', '${prefix}' / get_option('libdir'))
++pkgconf.set('includedir', '${prefix}' / get_option('includedir'))
+ pkgconf.set('VERSION', opus_version)
+ pkgconf.set('PC_BUILD', pc_build)
+ pkgconf.set('LIBM', libm.found() ? '-lm' : '')