[bash] Improve mawk detection (#3463)
* Use the all-compatible mawk `-W version` option.
https://github.com/junegunn/fzf/pull/3313#issuecomment-1747934690.
* Run the command and not a function consistently with #3462.
The version check bash code relies on the following mawk source code,
extracted from mawk 1.3.4 20230322.
```
version.c:
18- #include "init.h"
19- #include "patchlev.h"
20-
21: #define VERSION_STRING \
22- "mawk %d.%d%s %s\n\
23- Copyright 2008-2022,2023, Thomas E. Dickey\n\
24- Copyright 1991-1996,2014, Michael D. Brennan\n\n"
....
30- void
31- print_version(FILE *fp)
32- {
33: fprintf(fp, VERSION_STRING, PATCH_BASE, PATCH_LEVEL, PATCH_STRING, DATE_STRING);
34- fflush(fp);
35-
36- #define SHOW_RANDOM "random-funcs:"
patchlev.h:
13- /*
14- * $MawkId: patchlev.h,v 1.128 2023/03/23 00:23:57 tom Exp $
15- */
16: #define PATCH_BASE 1
17- #define PATCH_LEVEL 3
18- #define PATCH_STRING ".4"
19- #define DATE_STRING "20230322"
```
Co-authored-by: Junegunn Choi <junegunn.c@gmail.com>
