[libc] Add struct entry definition in addition to ENTRY according to POSIX. (#139773)

Author: lntue

libc/include/llvm-libc-types/ENTRY.h

@@ -9,7 +9,7 @@
 #ifndef LLVM_LIBC_TYPES_ENTRY_H
 #define LLVM_LIBC_TYPES_ENTRY_H
 
-typedef struct {
+typedef struct entry {
   char *key;
   void *data;
 } ENTRY;