disable parallel make for "fake"

Some ports are happy to _build_ in parallel, but fail during "make
fake". For example, vim and php.

We used to have a separate PARALLEL_INSTALL variable controlling
whether parallel flags were passed through there, added in r1.920,
removed in r1.1510.

I'm not convinced that parallel fake is enough of a win to be worth
restricting the number of ports that can use parallel build so I'd like
to remove it. (Apart from rare semi-broken ports which do a chunk of
compilation during "make fake", it's mostly going to be filesystem
access which doesn't parallelize brilliantly on OpenBSD at present
anyway).

Any OKs or objections to disabling it, so that MAKE_JOBS is only
passed through by infrastructure for build/test?

(If there's some individual port which would really benefit from
parallel install, it could always add to FAKE_FLAGS itself).

Index: bsd.port.mk
===================================================================
RCS file: /cvs/ports/infrastructure/mk/bsd.port.mk,v
diff -u -p -r1.1647 bsd.port.mk
--- bsd.port.mk 17 Jan 2026 22:30:08 -0000 1.1647
+++ bsd.port.mk 30 Mar 2026 09:47:11 -0000
@@ -488,7 +488,8 @@ MAKE_JOBS ?= 1

.if ${MAKE_JOBS} != 1
MAKE_FLAGS += ${PARALLEL_MAKE_FLAGS}
-ALL_FAKE_FLAGS += ${PARALLEL_MAKE_FLAGS}
+# various ports work with parallel build but fail with parallel install
+#ALL_FAKE_FLAGS += ${PARALLEL_MAKE_FLAGS}
.endif

# Here comes the part that sets BUILD_PACKAGES and various IGNORE* up.