tests/junit: add --env KEY=VAL flag for setting subprocess environment

Add a generic --env KEY=VAL CLI option (repeatable) to tests/junit.py
that injects environment variables into the test subprocess environment.
The flag mutates os.environ in the parent before mp.Pool is created, so
worker processes inherit the values via the existing init_process()
copy.

Useful for backend-specific runtime knobs that affect test behavior, for
example silencing chipStar runtime informational/warning lines that
JUnit otherwise classifies as test failures:

    make junit BACKENDS='/gpu/hip/ref ...' \
        JUNIT_ARGS='--env CHIP_LOGLEVEL=crit'

No changes to tests/junit_common.py.

Author: pvelesko

Makefile

@@ -831,7 +831,7 @@ NPROC_POOL ?= 1
 export NPROC_POOL
 
 run-% : $(OBJDIR)/%
-	@$(PYTHON) tests/junit.py --mode tap --ceed-backends $(BACKENDS) --nproc $(NPROC_TEST) --pool-size $(NPROC_POOL) --search '$(subsearch)' $(<:$(OBJDIR)/%=%)
+	@$(PYTHON) tests/junit.py --mode tap --ceed-backends $(BACKENDS) --nproc $(NPROC_TEST) --pool-size $(NPROC_POOL) --search '$(subsearch)' $(JUNIT_ARGS) $(<:$(OBJDIR)/%=%)
 
 # The test and prove targets can be controlled via pattern searches.  The
 # default is to run tests and those examples that have no external dependencies.
@@ -845,6 +845,8 @@ realsearch = $(search:%=%%)
 matched = $(foreach pattern,$(realsearch),$(filter $(OBJDIR)/$(pattern),$(tests) $(allexamples)))
 subsearch ?= .*
 JUNIT_BATCH ?= ''
+# Extra arguments forwarded to tests/junit.py (e.g. --env CHIP_LOGLEVEL=crit)
+JUNIT_ARGS ?=
 
 # Test core libCEED
 test : $(matched:$(OBJDIR)/%=run-%)
@@ -858,15 +860,15 @@ ctc-% : $(ctests);@$(foreach tst,$(ctests),$(tst) /cpu/$*;)
 # https://testanything.org/tap-specification.html
 prove : $(matched)
 	$(info Testing backends: $(BACKENDS))
-	$(PROVE) $(PROVE_OPTS) --exec '$(PYTHON) tests/junit.py' $(matched:$(OBJDIR)/%=%) :: --mode tap --ceed-backends $(BACKENDS) --nproc $(NPROC_TEST) --pool-size $(NPROC_POOL) --search '$(subsearch)'
+	$(PROVE) $(PROVE_OPTS) --exec '$(PYTHON) tests/junit.py' $(matched:$(OBJDIR)/%=%) :: --mode tap --ceed-backends $(BACKENDS) --nproc $(NPROC_TEST) --pool-size $(NPROC_POOL) --search '$(subsearch)' $(JUNIT_ARGS)
 # Run prove target in parallel
 prv : ;@$(MAKE) $(MFLAGS) V=$(V) prove
 
 prove-all :
 	+$(MAKE) prove realsearch=%
 
 junit-% : $(OBJDIR)/%
-	@printf "  %10s %s\n" TEST $(<:$(OBJDIR)/%=%); $(PYTHON) tests/junit.py --ceed-backends $(BACKENDS) --nproc $(NPROC_TEST) --pool-size $(NPROC_POOL) --search '$(subsearch)' --junit-batch $(JUNIT_BATCH) $(<:$(OBJDIR)/%=%)
+	@printf "  %10s %s\n" TEST $(<:$(OBJDIR)/%=%); $(PYTHON) tests/junit.py --ceed-backends $(BACKENDS) --nproc $(NPROC_TEST) --pool-size $(NPROC_POOL) --search '$(subsearch)' --junit-batch $(JUNIT_BATCH) $(JUNIT_ARGS) $(<:$(OBJDIR)/%=%)
 
 junit : $(matched:$(OBJDIR)/%=junit-%)
 

tests/junit.py

@@ -2,6 +2,26 @@
 from junit_common import *
 
 
+def parse_env_assignment(arg: str) -> Tuple[str, str]:
+    """Parse a KEY=VAL string from the --env flag.
+
+    Args:
+        arg (str): The KEY=VAL string
+
+    Returns:
+        Tuple[str, str]: (key, value) pair
+
+    Raises:
+        argparse.ArgumentTypeError: if `arg` is not in KEY=VAL form
+    """
+    if '=' not in arg:
+        raise argparse.ArgumentTypeError(f"--env expects KEY=VAL, got {arg!r}")
+    key, _, value = arg.partition('=')
+    if not key:
+        raise argparse.ArgumentTypeError(f"--env KEY must be non-empty, got {arg!r}")
+    return key, value
+
+
 def create_argparser() -> argparse.ArgumentParser:
     """Creates argument parser to read command line arguments
 
@@ -30,6 +50,11 @@ def create_argparser() -> argparse.ArgumentParser:
                         help='Search string to filter tests, using `re` package format')
     parser.add_argument('-v', '--verbose', action='store_true', default=False,
                         help='print details for all runs, not just failures')
+    parser.add_argument('--env', dest='extra_env', action='append', default=[], metavar='KEY=VAL',
+                        type=parse_env_assignment,
+                        help='Set an environment variable for test subprocesses; may be repeated. '
+                             'Useful for backend-specific runtime knobs (e.g. --env CHIP_LOGLEVEL=crit '
+                             'to silence chipStar runtime messages on stderr).')
     parser.add_argument('test', help='Test executable', nargs='?')
 
     return parser
@@ -198,6 +223,11 @@ def check_allowed_stdout(self, test: str) -> bool:
 if __name__ == '__main__':
     args = create_argparser().parse_args()
 
+    # Apply --env KEY=VAL settings to the parent environment so worker
+    # processes (which copy os.environ in init_process) inherit them.
+    for key, value in args.extra_env:
+        os.environ[key] = value
+
     result: TestSuite = run_tests(
         args.test,
         args.ceed_backends,