rtl : use a local std::mutex instead of the global mutex

Change-Id: I95a35fe451e459276dcb8c9b90d515d0a34fe36c
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/138318
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

sal/rtl/uuid.cxx

@@ -17,10 +17,10 @@
  *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
  */
 
+#include <mutex>
 #include <string.h>
 #include <stdlib.h>
 
-#include <osl/mutex.hxx>
 #include <rtl/random.h>
 #include <rtl/uuid.h>
 #include <rtl/digest.h>
@@ -108,7 +108,9 @@ extern "C" void SAL_CALL rtl_createUuid(sal_uInt8 *pTargetUUID ,
             return aPool;
         }();
 
-        osl::MutexGuard g(osl::Mutex::getGlobalMutex());
+        static std::mutex aMutex;
+
+        std::scoped_lock g(aMutex);
         if (rtl_random_getBytes(pool, pTargetUUID, 16) != rtl_Random_E_None)
         {
             abort();