When the local default shell is `dash`, the command script make/build.sh will fail with the following error messages.

```
$ sh make/build.sh --help
make/build.sh: 252: make/build.sh: Bad substitution
make/build.sh: 253: make/build.sh: Bad substitution
make/build.sh: 254: .: Can't open /build-support/build-common.sh
```

It is because my local `sh` command links to the `dash`. And the `dash` doesn't support the variables such as `BASH_SOURCE`.

```
$ ls -al /bin/*sh*
-rwxr-xr-x 1 root root 1113504 Jun 7 2019 /bin/bash
-rwxr-xr-x 1 root root 121432 Jan 25 2018 /bin/dash
lrwxrwxrwx 1 root root 4 Sep 26 2020 /bin/rbash -> bash
lrwxrwxrwx 1 root root 4 Sep 26 2020 /bin/sh -> dash
lrwxrwxrwx 1 root root 4 Sep 26 2020 /bin/sh.distrib -> dash
lrwxrwxrwx 1 root root 7 Sep 18 2020 /bin/static-sh -> busybox
```

It is good to state this situation in the documentation.