configure script failed on WSL

configure failed as following when I run it on WSL 1.

```
checking for version string... 20-internal-adhoc.yasuenag.jdk
configure: Found potential Boot JDK using configure arguments
configure: The command for java_to_test, which resolves as "/mnt/d/java/jdk-18/bin/java", can not be found.
configure: error: Cannot locate /mnt/d/java/jdk-18/bin/java
configure exiting with result code 1
```

fixpath.sh would attempt to add ".exe" (e.g. "java" -> "java.exe") if `wslpath -w" failed (returns non-zero value). However it returns zero even if the path does not exist in recent WSL (v0.61.4 at least).

WSL v0.60.0.0
```
$ wslpath -w silver-bullet
wslpath: silver-bullet: No such file or directory
$ echo $?
1
```

WSL v0.61.4.0
```
$ wslpath -w silver-bullet
silver-bullet
$ echo $?
0
```

We should add ".exe" at the tail of path regardless of return value from wslpath.