Fix out-of-tree builds for blake2
diff --git a/Makefile.pre.in b/Makefile.pre.in
index e17fe77..04499dc 100644
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -541,7 +541,7 @@
# 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 @@
$(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