LaTeX error when building a file from xindy documentation

[jfbu]

I hope I am not bothering too much, but what shell is actually used?

This Makefile

.PHONY: test

test:
	echo -n '\ftest'
	@echo -n '\ftest' > test


behaves this way

$ make test
echo -n '\ftest'
\ftest(base)

which shows the newline is indeed remove from -n (because (base) is some PS1 stuff)
and the \f escape is not interpreted.

However the second line of recipe redirects to test file and the produced test file contains

-n <CTRL-L>test

showing that -n is not recognized and the \f is interpreted as an escape.

I thought perhaps there is a different behaviour between my built-in
echo in bash shell and /bin/echo but there is none.

Then I did this

$ /bin/sh
sh-3.2$ echo -n '\ftest'
-n 
   test
sh-3.2$

showing that -n is not understood and \f escape is interpreted.

Which makes me suspect the explanation is that the Makefile
does not use my default user shell bash, but the sh shell.

Best,
Jean-François