Fallback on PYTHON path in Makefile

- Change default PYTHON in Makefile to be ranked choice
- Fix `PYTHON_VERSION` target that expects just a word
- Use native GNU Make `$(subst ,,)` instead of `sed`
- Add 'version-for-buildyml' target to simplify ci

If I understand correctly, this change should make
'$(PYTHON)' work how we want it to everywhere. Before
this change, on develpers' machines that don't have
a 'python3.9' in their path, make would fail. With this
change, we will prefer python3.9 if it's available, but
we'll take python3 otherwise.

Makefile

@@ -1,6 +1,6 @@
 -include awx/ui_next/Makefile
 
-PYTHON ?= python3.9
+PYTHON := $(notdir $(shell for i in python3.9 python3; do command -v $$i; done|sed 1q))
 DOCKER_COMPOSE ?= docker-compose
 OFFICIAL ?= no
 NODE ?= node
@@ -606,7 +606,18 @@ VERSION:
 	@echo "awx: $(VERSION)"
 
 PYTHON_VERSION:
-	@echo "$(PYTHON)" | sed 's:python::'
+	@echo "$(subst python,,$(PYTHON))"
+
+.PHONY: version-for-buildyml
+version-for-buildyml:
+	@echo $(firstword $(subst +, ,$(VERSION)))
+# version-for-buildyml prints a special version string for build.yml,
+# chopping off the sha after the '+' sign.
+# tools/ansible/build.yml was doing this: make print-VERSION | cut -d + -f -1
+# This does the same thing in native make without
+# the pipe or the extra processes, and now the pb does `make version-for-buildyml`
+# Example:
+# 	22.1.1.dev38+g523c0d9781 becomes 22.1.1.dev38
 
 .PHONY: Dockerfile
 ## Generate Dockerfile for awx image
@@ -658,6 +669,7 @@ messages:
 	fi; \
 	$(PYTHON) manage.py makemessages -l en_us --keep-pot
 
+.PHONY: print-%
 print-%:
 	@echo $($*)
 

tools/ansible/build.yml

@@ -4,8 +4,7 @@
   gather_facts: true
   tasks:
     - name: Get version from SCM if not explicitly provided
-      shell: |
-        make print-VERSION | cut -d + -f -1
+      command: make version-for-buildyml
       args:
         chdir: '../../'
       register: scm_version