build: delete/replace clang warning pragmas

- delete redundant warning suppressions for `-Wformat-nonliteral`.
  This now relies on `CURL_PRINTF()` and it's theoratically possible
  that this macro isn't active but the warning is. We're ignoring this
  as a corner-case here.

- replace two pragmas with code changes to avoid the warnings.

Follow-up to aee4ebe591 #12803
Follow-up to 0923012758 #12540
Follow-up to 3829759bd0 #12489

Reviewed-by: Daniel Stenberg
Closes #12812

src/tool_setopt.c

@@ -240,22 +240,11 @@ static char *c_escape(const char *str, curl_off_t len)
       if(p && *p)
         result = curlx_dyn_addn(&escaped, to + 2 * (p - from), 2);
       else {
-        const char *format = "\\x%02x";
-
-        if(len > 1 && ISXDIGIT(s[1])) {
-          /* Octal escape to avoid >2 digit hex. */
-          format = "\\%03o";
-        }
-
-#ifdef __clang__
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wformat-nonliteral"
-#endif
-        result = curlx_dyn_addf(&escaped, format,
+        result = curlx_dyn_addf(&escaped,
+                                /* Octal escape to avoid >2 digit hex. */
+                                (len > 1 && ISXDIGIT(s[1])) ?
+                                  "\\%03o" : "\\x%02x",
                                 (unsigned int) *(unsigned char *) s);
-#ifdef __clang__
-#pragma clang diagnostic pop
-#endif
       }
     }
   }