Makefile.uk: Ensure consistent Python binary name

Previously Makefile.uk used `python` and `python3` interchangeably which
caused unexpected issues on misconfigured systems where these two do not
point to the same binary.
This change fixes this oversight by using `python` everywhere.

Signed-off-by: Andrei Tatar <[email protected]>
Reviewed-by: Stefan Jumarea <[email protected]>
Reviewed-by: Radu Nichita <[email protected]>
Approved-by: Razvan Deaconescu <[email protected]>
GitHub-Closes: #22

Makefile.uk

@@ -497,7 +497,7 @@ PYTHON_ROOTFS = $(APP_BASE)/$(path)
 $(PYTHON_ROOTFS)/.keep: $(LIBPYTHON3_BUILD)/.origin
 	@test $(LIBPYTHON3_VERSION) = `python -V | cut -d' ' -f2 | cut -d. -f1,2` || \
 		(echo -e "WARNING: creating virtualenv with wrong python version, pip might not work correctly\nPress return to continue" && read)
-	python3 -m venv $(PYTHON_ROOTFS)
+	python -m venv $(PYTHON_ROOTFS)
 	find "$(PYTHON_ROOTFS)" -type d -name '__pycache__' | xargs rm -rf
 	touch $@
 
@@ -516,7 +516,7 @@ $(PYTHON_ROOTFS)/.done: $(PYTHON_ROOTFS)/.configured
 $(PYTHON_ROOTFS)/.compiled: python-rootfs
 	test $(LIBPYTHON3_VERSION) = `python -V | cut -d' ' -f2 | cut -d. -f1,2` || \
 		(echo "ERROR: local Python version is not $(LIBPYTHON3_VERSION), cannot compile .py files" && false)
-	python3 -m compileall -x 'lib2to3/|test/bad' "$(PYTHON_ROOTFS)/lib"
+	python -m compileall -x 'lib2to3/|test/bad' "$(PYTHON_ROOTFS)/lib"
 	touch $@
 
 .PHONY: python-rootfs