pipewire: use meson options for installed_tests

pkgs/development/libraries/pipewire/default.nix

@@ -65,9 +65,6 @@ stdenv.mkDerivation rec {
     ./installed-tests-path.patch
   ];
 
-  postPatch = ''
-    substituteInPlace meson.build --subst-var-by installed_tests_dir "$installedTests"
-  '';
 
   nativeBuildInputs = [
     doxygen
@@ -99,6 +96,7 @@ stdenv.mkDerivation rec {
     "-Dexamples=true" # only needed for `pipewire-media-session`
     "-Dudevrulesdir=lib/udev/rules.d"
     "-Dinstalled_tests=true"
+    "-Dinstalled_test_prefix=${placeholder "installedTests"}"
     "-Dlibpulse-path=${placeholder "pulse"}/lib"
     "-Dlibjack-path=${placeholder "jack"}/lib"
     "-Dgstreamer=${mesonBool gstreamerSupport}"

pkgs/development/libraries/pipewire/installed-tests-path.patch

@@ -1,5 +1,5 @@
 diff --git a/meson.build b/meson.build
-index ffee41b4..b75921f9 100644
+index ffee41b4..bab6f019 100644
 --- a/meson.build
 +++ b/meson.build
 @@ -318,8 +318,8 @@ alsa_dep = (get_option('pipewire-alsa')
@@ -8,8 +8,22 @@ index ffee41b4..b75921f9 100644
  
 -installed_tests_metadir = join_paths(pipewire_datadir, 'installed-tests', pipewire_name)
 -installed_tests_execdir = join_paths(pipewire_libexecdir, 'installed-tests', pipewire_name)
-+installed_tests_metadir = join_paths('@installed_tests_dir@', 'share', 'installed-tests', pipewire_name)
-+installed_tests_execdir = join_paths('@installed_tests_dir@', 'libexec', 'installed-tests', pipewire_name)
++installed_tests_metadir = join_paths(get_option('installed_test_prefix'), 'share', 'installed-tests', pipewire_name)
++installed_tests_execdir = join_paths(get_option('installed_test_prefix'), 'libexec', 'installed-tests', pipewire_name)
  installed_tests_enabled = get_option('installed_tests')
  installed_tests_template = files('template.test.in')
  
+diff --git a/meson_options.txt b/meson_options.txt
+index f03033c3..32df6c53 100644
+--- a/meson_options.txt
++++ b/meson_options.txt
+@@ -18,6 +18,9 @@ option('installed_tests',
+        description: 'Install manual and automated test executables',
+        type: 'boolean',
+        value: false)
++option('installed_test_prefix',
++       description: 'Prefix for installed tests',
++       type: 'string')
+ option('gstreamer',
+        description: 'Build GStreamer plugins',
+        type: 'boolean',