soup: Ensure that libsoup RPATHs are added with Homebrew too

With the old method of adding build RPATHs, only the libsoup as
a subproject was supported. However, it's possible to use Homebrew for
libsoup too by adding libsoup as a dependency to the target (even
though we don't link to it).

Apple ld will not add a LC_LOAD_DYLIB entry for a library unless there
are symbols that need it because meson passes `-dead_strip_dylibs`, so
we can do this without issue.

As a bonus, this ensures the correct build RPATHs in all cases.

Additionally, we still need to explicitly add an LC_RPATH for the
installed case.

Fixes https://gitlab.freedesktop.org/gstreamer/gstreamer/-/issues/4027

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/8403>

subprojects/gst-plugins-good/ext/adaptivedemux2/meson.build

@@ -157,6 +157,7 @@ if host_system == 'windows'
 else
   if default_library in ['static', 'both']
     # Static plugin links to libsoup directly at build time
+    assert(soup_linked_target)
     adaptivedemux2_static = static_library('gstadaptivedemux2',
       c_args: [adaptive_args, soup_linked_target_args],
       dependencies: [adaptive_deps, soup_linked_target_deps],
@@ -165,7 +166,7 @@ else
   if default_library in ['shared', 'both']
     adaptivedemux2_shared = shared_library('gstadaptivedemux2',
       c_args: adaptive_args,
-      dependencies: adaptive_deps,
+      dependencies: [adaptive_deps, soup_dlopen_target_deps],
       kwargs: adaptive_kwargs + soup_dlopen_target_kwargs)
   endif
 endif

subprojects/gst-plugins-good/ext/meson.build

@@ -18,6 +18,7 @@ soup_ver_opt = get_option('soup-version')
 default_library = get_option('default_library')
 soup_linked_target = host_system == 'windows' or default_library != 'shared'
 soup_lookup_dep = get_option('soup-lookup-dep') or soup_linked_target
+soup_dlopen_target_deps = []
 soup_dlopen_target_kwargs = {}
 
 if get_option('soup').allowed() or get_option('adaptivedemux2').allowed()
@@ -43,16 +44,22 @@ if get_option('soup').allowed() or get_option('adaptivedemux2').allowed()
     endif
   endif
 
-  # Hack to set the right RPATH for making dlopen() work inside the devenv on
+  # Hack to set the LC_RPATH for making dlopen() work, since meson will only
-  # macOS when using libsoup as a subproject.
+  # add that for deps that are in the list of dependencies. We also need to add
+  # install_rpath to cover the installation case. Every other dep is loaded via
+  # absolute LC_LOAD_DYLIB entries.
   if host_system == 'darwin'
     foreach dep : [libsoup3_dep, libsoup2_dep]
-      if dep.found() and dep.type_name() == 'internal'
+      if not dep.found()
-        soup_dlopen_target_kwargs += {
+        continue
-          'build_rpath': '@loader_path/../../../libsoup-' + dep.version() / 'libsoup',
-        }
-        break
       endif
+      soup_dlopen_target_deps += [dep]
+      if dep.type_name() == 'internal'
+        soup_dlopen_target_kwargs += {'install_rpath': '@loader_path/..'}
+      else
+        soup_dlopen_target_kwargs += {'install_rpath': dep.get_variable('libdir')}
+      endif
+      break
     endforeach
   endif
 endif

subprojects/gst-plugins-good/ext/soup/meson.build

@@ -71,7 +71,7 @@ else
   if default_library in ['shared', 'both']
     gstsouphttpsrc_shared = shared_library('gstsoup',
       c_args : soup_library_c_args,
-      dependencies : soup_library_deps,
+      dependencies : soup_library_deps + soup_dlopen_target_deps,
       kwargs: soup_library_kwargs + soup_dlopen_target_kwargs,
     )
   endif