Fix issue 17413: Prevent deadlock in the GC init

If the program during initialization in the pressing memory
environment died with the Error thrown by the GC, GC would
not be usable anymore. However, dso registry unregistration
will try to removeRanges. This would cause a deadlock in the GC,
preventing the exit of the program. This commit prevents GC entering
the recursive lock from the chain GC.fullcollect() -> Error -> dso_registry
-> GC.removeRange.

Author: Burgos

src/gc/impl/conservative/gc.d

@@ -1093,7 +1093,7 @@ class ConservativeGC : GC
 
     void removeRange(void *p) nothrow @nogc
     {
-        if (!p)
+        if (!p || _isLocked)
         {
             return;
         }
@@ -2374,6 +2374,7 @@ struct Gcx
 
         {
             // lock roots and ranges around suspending threads b/c they're not reentrant safe
+            ConservativeGC._isLocked = true;
             rangesLock.lock();
             rootsLock.lock();
             scope (exit)
@@ -2395,6 +2396,7 @@ struct Gcx
             markAll(nostack);
 
             thread_processGCMarks(&isMarked);
+            ConservativeGC._isLocked = false;
             thread_resumeAll();
         }