Rename build-details.json to allow libpython3.14-stdlib to be multiarch
co-installable. PEP 739 is planned to be updated to allow this.

Bug-Debian: https://bugs.debian.org/1121810
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -797,11 +797,11 @@
 
 .PHONY: build_all
 build_all:	check-clean-src check-app-store-compliance $(BUILDPYTHON) platform sharedmods \
-		gdbhooks Programs/_testembed scripts checksharedmods rundsymutil build-details.json
+		gdbhooks Programs/_testembed scripts checksharedmods rundsymutil build-details_$(MULTIARCH).json
 
 .PHONY: build_wasm
 build_wasm: check-clean-src $(BUILDPYTHON) platform sharedmods \
-		python-config checksharedmods build-details.json
+		python-config checksharedmods build-details_$(MULTIARCH).json
 
 .PHONY: build_emscripten
 build_emscripten: build_wasm web_example web_example_pyrepl_jspi
@@ -1012,8 +1012,8 @@
 		exit 1 ; \
 	fi
 
-build-details.json: pybuilddir.txt
-	$(RUNSHARED) $(PYTHON_FOR_BUILD) $(srcdir)/Tools/build/generate-build-details.py `cat pybuilddir.txt`/build-details.json
+build-details_$(MULTIARCH).json: pybuilddir.txt
+	$(RUNSHARED) $(PYTHON_FOR_BUILD) $(srcdir)/Tools/build/generate-build-details.py `cat pybuilddir.txt`/build-details_$(MULTIARCH).json
 
 # Build static library
 $(LIBRARY): $(LIBRARY_OBJS)
@@ -2812,7 +2812,7 @@
 	done
 	$(INSTALL_DATA) `cat pybuilddir.txt`/_sysconfigdata_$(ABIFLAGS)_$(MACHDEP)_$(MULTIARCH).py $(DESTDIR)$(LIBDEST); \
 	$(INSTALL_DATA) `cat pybuilddir.txt`/_sysconfig_vars_$(ABIFLAGS)_$(MACHDEP)_$(MULTIARCH).json $(DESTDIR)$(LIBDEST); \
-	$(INSTALL_DATA) `cat pybuilddir.txt`/build-details.json $(DESTDIR)$(LIBDEST); \
+	$(INSTALL_DATA) `cat pybuilddir.txt`/build-details_$(MULTIARCH).json $(DESTDIR)$(LIBDEST); \
 	$(INSTALL_DATA) $(srcdir)/LICENSE $(DESTDIR)$(LIBDEST)/LICENSE.txt
 	@ # If app store compliance has been configured, apply the patch to the
 	@ # installed library code. The patch has been previously validated against
--- a/Lib/test/test_build_details.py
+++ b/Lib/test/test_build_details.py
@@ -130,7 +130,7 @@
                 dirname = os.path.join(projectdir, f.read())
         else:
             dirname = sysconfig.get_path('stdlib')
-        return os.path.join(dirname, 'build-details.json')
+        return os.path.join(dirname, f'build-details_{sys.implementation._multiarch}.json')
 
     @property
     def contents(self):