Makefile always regenerates `build-details.json`

[colesbury]

The Makefile target that generates build-details.json has an incorrect target so it's re-run for every action. The generated file is in:

`cat pybuilddir.txt`/build-details.json

For example, on my machine that evaluates to:

build/lib.linux-x86_64-3.14/build-details.json

cpython/Makefile.pre.in

Lines 939 to 940 in 6131707

	build-details.json: pybuilddir.txt
	$(RUNSHARED) $(PYTHON_FOR_BUILD) $(srcdir)/Tools/build/generate-build-details.py `cat pybuilddir.txt`/build-details.json

Linked PRs

• gh-131556: Fix build-details.json Makefile target #131558
• GH-131556: calculate PYBUILDDIR in the makefile instead of sysconfig #131761