In musl libc there is no struct mallinfo and no function mallinf()

--- a/src/OSD/OSD_MemInfo.cxx.orig	2022-10-06 09:21:55.466236104 +0200
+++ b/src/OSD/OSD_MemInfo.cxx	2022-10-06 09:25:34.105323581 +0200
@@ -188,12 +188,16 @@ void OSD_MemInfo::Update()
     #endif
   #endif
 
+  #if defined(__GLIBC__)
   #ifdef HAS_MALLINFO2
     const struct mallinfo2 aMI = mallinfo2();
   #else
     const struct mallinfo aMI = mallinfo();
   #endif
     myCounters[MemHeapUsage] = aMI.uordblks;
+  #else
+    myCounters[MemHeapUsage] = 0;
+  #endif
   }
 
   if (!IsActive (MemVirtual)
