unix: update Makefile.pre.in patch for Python 3.9

The line above the patched line changed in 3.9 and warrants yet another
variant of this patch.

cpython-unix/build-cpython.sh

@@ -114,7 +114,7 @@ diff --git a/Makefile.pre.in b/Makefile.pre.in
  platform: $(BUILDPYTHON) pybuilddir.txt
  	$(RUNSHARED) $(PYTHON_FOR_BUILD) -c 'import sys ; from sysconfig import get_platform ; print("%s-%d.%d" % (get_platform(), *sys.version_info[:2]))' >platform
 EOF
-    else
+    elif [ "${PYTHON_MAJMIN_VERSION}" = "3.8" ]; then
         patch -p1 <<"EOF"
 diff --git a/Makefile.pre.in b/Makefile.pre.in
 --- a/Makefile.pre.in
@@ -126,6 +126,21 @@ diff --git a/Makefile.pre.in b/Makefile.pre.in
 -	$(LINKCC) $(PY_CORE_LDFLAGS) $(LINKFORSHARED) -o $@ Programs/python.o $(BLDLIBRARY) $(LIBS) $(MODLIBS) $(SYSLIBS)
 +	$(LINKCC) $(PY_CORE_LDFLAGS) $(LINKFORSHARED) -o $@ Programs/python.o $(BLDLIBRARY) $(LIBS) $(SYSLIBS)
  
+ platform: $(BUILDPYTHON) pybuilddir.txt
+ 	$(RUNSHARED) $(PYTHON_FOR_BUILD) -c 'import sys ; from sysconfig import get_platform ; print("%s-%d.%d" % (get_platform(), *sys.version_info[:2]))' >platform
+EOF
+    else
+        patch -p1 <<"EOF"
+diff --git a/Makefile.pre.in b/Makefile.pre.in
+--- a/Makefile.pre.in
++++ b/Makefile.pre.in
+@@ -563,7 +563,7 @@ clinic: check-clean-src $(srcdir)/Modules/_blake2/blake2s_impl.c
+
+ # Build the interpreter
+ $(BUILDPYTHON):	Programs/python.o $(LIBRARY) $(LDLIBRARY) $(PY3LIBRARY) $(EXPORTSYMS)
+-	$(LINKCC) $(PY_CORE_LDFLAGS) $(LINKFORSHARED) -o $@ Programs/python.o $(BLDLIBRARY) $(LIBS) $(MODLIBS) $(SYSLIBS)
++	$(LINKCC) $(PY_CORE_LDFLAGS) $(LINKFORSHARED) -o $@ Programs/python.o $(BLDLIBRARY) $(LIBS) $(SYSLIBS)
+
  platform: $(BUILDPYTHON) pybuilddir.txt
  	$(RUNSHARED) $(PYTHON_FOR_BUILD) -c 'import sys ; from sysconfig import get_platform ; print("%s-%d.%d" % (get_platform(), *sys.version_info[:2]))' >platform
 EOF