github: use CI build number as git tag

This fixes dirty builds changing reported firmware size on CI and allows
verifying the build number of a firmware at runtime. It uses a new
feature in the MicroPython 1.20 makeversionheader.py script that looks
at environment variables to override the versions instead of using
`git describe`.

Fixes: https://github.com/pybricks/pybricks-micropython/issues/123

.github/build-each-commit.py

@@ -15,6 +15,11 @@
 
 PYBRICKS_PATH = os.environ.get("PYBRICKS_PATH", ".")
 
+GITHUB_RUN_NUMBER = os.environ.get("GITHUB_RUN_NUMBER")
+
+if GITHUB_RUN_NUMBER:
+    os.putenv("MICROPY_GIT_TAG", f"ci-build-{GITHUB_RUN_NUMBER}")
+
 
 parser = argparse.ArgumentParser()
 parser.add_argument("hub", metavar="<hub>")
@@ -45,6 +50,7 @@
 ):
     print("Checking out", commit.hexsha[:8], f'"{commit.summary}"', flush=True)
     pybricks.git.checkout(commit.hexsha)
+    os.putenv("MICROPY_GIT_HASH", commit.hexsha[:8])
 
     # update only required submodules
     pybricks.git.submodule("update", "--init", "micropython")

.github/build-missing-commits.py

@@ -21,6 +21,11 @@
 
 HUBS = ["movehub", "cityhub", "technichub", "primehub", "essentialhub", "nxt"]
 
+GITHUB_RUN_NUMBER = os.environ.get("GITHUB_RUN_NUMBER")
+
+if GITHUB_RUN_NUMBER:
+    os.putenv("MICROPY_GIT_TAG", f"ci-build-{GITHUB_RUN_NUMBER}")
+
 print("Building commits...")
 
 try:
@@ -66,6 +71,7 @@
     # Checkout the Pybricks MicroPython commit for processing
     print("Checking out:", commit.hexsha)
     pybricks.git.checkout(commit.hexsha)
+    os.putenv("MICROPY_GIT_HASH", commit.hexsha[:8])
 
     # update required submodules
     print("Checking out submodules")