Change static variables accessed concurrently to thread_local (#4980)

include/ccf/crypto/entropy.h

@@ -57,7 +57,7 @@ namespace crypto
   private:
     static int get_drng_support()
     {
-      static int drng_features = -1;
+      thread_local int drng_features = -1;
 
       /* So we don't call cpuid multiple times for the same information */
       if (drng_features == -1)

include/ccf/pal/hardware_info.h

@@ -26,7 +26,7 @@ namespace ccf::pal
 
   static bool is_intel_cpu()
   {
-    static int intel_cpu = -1;
+    thread_local int intel_cpu = -1;
 
     if (intel_cpu == -1)
     {