PGXS "check" target forcing an install ?

I've noted that upgrading from PostgreSQL 9.3 to 9.5 I'm suddenly
unable to specify a "check" rule in the Makefile that includes the
PGXS one. The error is:

$ make check
rm -rf ''/tmp_install
make -C '/home/postgresql-9.5/lib/pgxs/src/makefiles/../..' DESTDIR=''/tmp_install install
make[1]: Entering directory `/home/postgresql-9.5/lib/pgxs'
make[1]: *** No rule to make target `install'. Stop.
make[1]: Leaving directory `/home/postgresql-9.5/lib/pgxs'
make: *** [temp-install] Error 2

I tracked the dangerous -rf to come from Makefile.global and it's empty
string being due to abs_top_builddir not being define in my own Makefile.

But beside that, which I can probably fix, it doesn't sound correct
that a "check" rule insists in finding an "install" rule. I'm also
surprised that there's no warning coming out from the "make" invocation
given I'm defining a "check" rule myself (after inclusion).

Minimal Makefile reproducing the error:

PGXS := /home/postgresql-9.3/lib/pgxs/src/makefiles/pgxs.mk # succeeds
PGXS := /home/postgresql-9.5/lib/pgxs/src/makefiles/pgxs.mk # fails
include $(PGXS)
check:
echo "Checking"

To verify, just run "make check"

--strk;

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