Testsuite failures of gawk 5.2.0 on riscv64

[Letu Ren]

Hi, I'm trying to build gawk on riscv64. However, `make check` fails
with 4 failures. After looking through the archive of bug-gawk, I
noticed that inf-nan-torture has been fixed in master branch. I tried
with the latest git version of gawk, and there are still three
failures.

```
============== _commas =============
--- /home/fanta/source/gawk/test/commas.ok      2022-09-17
15:20:01.069212252 +0800
+++ _commas     2022-09-22 00:56:15.304597780 +0800
@@ -1,2 +1,2 @@
-123,456,789
-123,456,789.000000
+123456789
+123456789.000000
============== _mbstr1 =============
--- /home/fanta/source/gawk/test/mbstr1.ok      2022-09-17
15:20:01.265859569 +0800
+++ _mbstr1     2022-09-22 00:56:19.464188523 +0800
@@ -1,3 +1,2 @@
-gawk: mbstr1.awk:2: warning: Invalid multibyte data detected. There
may be a mismatch between your data and your locale
4
1
============== _mbstr2 =============
--- /home/fanta/source/gawk/test/mbstr2.ok      2022-09-17
15:20:01.265859569 +0800
+++ _mbstr2     2022-09-22 00:56:19.560845679 +0800
@@ -1,5 +1,4 @@
2007
-gawk: mbstr2.awk:1: (FILENAME=- FNR=2) warning: Invalid multibyte
data detected. There may be a mismatch between your data and your
locale
2007
2007
2007
```

My build options are `./configure --prefix=/usr --libexecdir=/usr/lib
--sysconfdir=/etc --without-libsigsegv`. This configuration works well
on x86_64.

Does anybody know why these tests fail? Thanks in advance.

Letu Ren