unittests: fix -Wnarrowing build errors

src/common/dwarf/dwarf2diehandler.cc

Index: src/common/dwarf/dwarf2diehandler.cc
diff --git a/src/common/dwarf/dwarf2diehandler.cc b/src/common/dwarf/dwarf2diehandler.cc
index 20c15fa9d10262d69a2b6daf65115a4c117f0427..94542b5ea9e87eb46b7fc6a5cfaf9ff1ac8c97d9 100644
--- a/src/common/dwarf/dwarf2diehandler.cc
+++ b/src/common/dwarf/dwarf2diehandler.cc
@@ -32,6 +32,7 @@
 // See dwarf2diehandler.h for details.
 
 #include <assert.h>
+#include <stdint.h>
 
 #include <string>
 
@@ -167,7 +168,7 @@ void DIEDispatcher::ProcessAttributeReference(uint64 offset,
 void DIEDispatcher::ProcessAttributeBuffer(uint64 offset,
                                            enum DwarfAttribute attr,
                                            enum DwarfForm form,
-                                           const char* data,
+                                           const uint8_t *data,
                                            uint64 len) {
   HandlerStack &current = die_handlers_.top();
   // This had better be an attribute of the DIE we were meant to handle.