servo: Merge #20310 - Update the MULTIPROCESS static when changing default options (from fabricedesre:opt-multiprocess); r=jdm

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When the options are set not from the command line but by calling `set_defaults()` which is common for embedders, the MULTIPROCESS static is not set, and so the setting is ignored. This patch fixes that.

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Source-Repo: https://github.com/servo/servo
Source-Revision: b93f153ed59fb993af306bd8c540887196021f87

--HG--
extra : subtree_source : https%3A//hg.mozilla.org/projects/converted-servo-linear
extra : subtree_revision : 6c85e2e3c9e0ef460304606c14edc356bdd721af

servo/components/config/opts.rs

@@ -911,6 +911,9 @@ lazy_static! {
 }
 
 pub fn set_defaults(opts: Opts) {
+    // Set the static to the new default value.
+    MULTIPROCESS.store(opts.multiprocess, Ordering::SeqCst);
+
     unsafe {
         assert!(DEFAULT_OPTIONS.is_null());
         assert_ne!(DEFAULT_OPTIONS, INVALID_OPTIONS);