VMS: fix collected error strings

It turns out that on VMS, strerror() returns messages with added
spaces at the end.

We wouldn't had noticed if it wasn't for perl trimming those spaces
off for its own sake and thereby having test/recipes/02-test_errstr.t
fail on VMS.

The safe fix is to do the same trimming ourselves.
Reviewed-by: NPaul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/7701)

(cherry picked from commit 9f15e5b911ba6053e09578f190354568e01c07d7)

crypto/err/err.c

@@ -19,6 +19,7 @@
 #include <openssl/bio.h>
 #include <openssl/opensslconf.h>
 #include "internal/thread_once.h"
+#include "internal/ctype.h"
 
 static int err_load_strings(const ERR_STRING_DATA *str);
 
@@ -217,13 +218,24 @@ static void build_SYS_str_reasons(void)
         str->error = ERR_PACK(ERR_LIB_SYS, 0, i);
         if (str->string == NULL) {
             if (openssl_strerror_r(i, cur, sizeof(strerror_pool) - cnt)) {
-                size_t l = strlen(cur) + 1;
+                size_t l = strlen(cur);
 
                 str->string = cur;
                 cnt += l;
                 if (cnt > sizeof(strerror_pool))
                     cnt = sizeof(strerror_pool);
                 cur += l;
+
+                /*
+                 * VMS has an unusual quirk of adding spaces at the end of
+                 * some (most? all?) messages.  Lets trim them off.
+                 */
+                while (ossl_isspace(cur[-1])) {
+                    cur--;
+                    cnt--;
+                }
+                *cur++ = '\0';
+                cnt++;
             }
         }
         if (str->string == NULL)