Fix out-of-tree builds for blake2

Makefile.pre.in

@@ -541,7 +541,7 @@ coverage-report:
 # Run "Argument Clinic" over all source files
 # (depends on python having already been built)
 .PHONY=clinic
-clinic: $(BUILDPYTHON) Modules/_blake2/blake2s_impl.c
+clinic: $(BUILDPYTHON) $(srcdir)/Modules/_blake2/blake2s_impl.c
 	$(RUNSHARED) $(PYTHON_FOR_BUILD) ./Tools/clinic/clinic.py --make
 
 # Build the interpreter
@@ -572,9 +572,9 @@ Modules/_math.o: Modules/_math.c Modules/_math.h
 	$(CC) -c $(CCSHARED) $(PY_CORE_CFLAGS) -o $@ $<
 
 # blake2s is auto-generated from blake2b
-Modules/_blake2/blake2s_impl.c: $(BUILDPYTHON) Modules/_blake2/blake2b_impl.c Modules/_blake2/blake2b2s.py
-	$(RUNSHARED) $(PYTHON_FOR_BUILD) Modules/_blake2/blake2b2s.py
-	$(RUNSHARED) $(PYTHON_FOR_BUILD) Tools/clinic/clinic.py -f $@
+$(srcdir)/Modules/_blake2/blake2s_impl.c: $(BUILDPYTHON) $(srcdir)/Modules/_blake2/blake2b_impl.c $(srcdir)/Modules/_blake2/blake2b2s.py
+	$(RUNSHARED) $(PYTHON_FOR_BUILD) $(srcdir)/Modules/_blake2/blake2b2s.py
+	$(RUNSHARED) $(PYTHON_FOR_BUILD) $(srcdir)/Tools/clinic/clinic.py -f $@
 
 # Build the shared modules
 # Under GNU make, MAKEFLAGS are sorted and normalized; the 's' for

setup.py

@@ -889,8 +889,8 @@ class PyBuildExt(build_ext):
         exts.append( Extension('_sha1', ['sha1module.c'],
                                depends=['hashlib.h']) )
 
-        blake2_deps = [os.path.join('_blake2', 'impl', name)
-                       for name in os.listdir('Modules/_blake2/impl')]
+        blake2_deps = glob(os.path.join(os.getcwd(), srcdir,
+                                        'Modules/_blake2/impl/*'))
         blake2_deps.append('hashlib.h')
 
         blake2_macros = []