Share /gnu/store in the BubbleWrap container and remove FHS mounts.

This is a Guix-specific patch not meant to be upstreamed.
diff --git a/Source/WebKit/UIProcess/Launcher/glib/BubblewrapLauncher.cpp b/Source/WebKit/UIProcess/Launcher/glib/BubblewrapLauncher.cpp
index f0a5e4b05dff..88b11f806968 100644
--- a/Source/WebKit/UIProcess/Launcher/glib/BubblewrapLauncher.cpp
+++ b/Source/WebKit/UIProcess/Launcher/glib/BubblewrapLauncher.cpp
@@ -854,27 +854,12 @@ GRefPtr<GSubprocess> bubblewrapSpawn(GSubprocessLauncher* launcher, const Proces
         "--ro-bind", "/sys/dev", "/sys/dev",
         "--ro-bind", "/sys/devices", "/sys/devices",
 
-        "--ro-bind-try", "/usr/share", "/usr/share",
-        "--ro-bind-try", "/usr/local/share", "/usr/local/share",
         "--ro-bind-try", DATADIR, DATADIR,
-
-        // We only grant access to the libdirs webkit is built with and
-        // guess system libdirs. This will always have some edge cases.
-        "--ro-bind-try", "/lib", "/lib",
-        "--ro-bind-try", "/usr/lib", "/usr/lib",
-        "--ro-bind-try", "/usr/local/lib", "/usr/local/lib",
         "--ro-bind-try", LIBDIR, LIBDIR,
-#if CPU(ADDRESS64)
-        "--ro-bind-try", "/lib64", "/lib64",
-        "--ro-bind-try", "/usr/lib64", "/usr/lib64",
-        "--ro-bind-try", "/usr/local/lib64", "/usr/local/lib64",
-#else
-        "--ro-bind-try", "/lib32", "/lib32",
-        "--ro-bind-try", "/usr/lib32", "/usr/lib32",
-        "--ro-bind-try", "/usr/local/lib32", "/usr/local/lib32",
-#endif
-
         "--ro-bind-try", PKGLIBEXECDIR, PKGLIBEXECDIR,
+
+        // Bind mount the store inside the WebKitGTK sandbox.
+        "--ro-bind", "@storedir@", "@storedir@",
     };
 
     if (launchOptions.processType == ProcessLauncher::ProcessType::DBusProxy) {
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