Add flush for better debugging in run_tests.py #3947

Job	Run time
pre-commit / pre-commit	1m 9s
mac / clang-build (Release)	1m 48s
windows / clang-build	2m 3s
mac / clang-build (Debug)	19m 38s
windows / msvc-build (Debug)	2m 49s
windows / msvc-build (Release)	1m 40s
ubuntu / gcc-build (ubuntu-24.04-arm, Release)	1m 10s
ubuntu / clang-build (ubuntu-24.04-arm)	1m 11s
ubuntu / gcc-build (ubuntu-24.04, Release)	1m 15s
ubuntu / gcc-build (ubuntu-24.04, Debug)	57s
ubuntu / gcc-build (ubuntu-24.04-arm, Debug)	1m 16s
ubuntu / clang-build (ubuntu-24.04)	52s
ubuntu / clang-test (ubuntu-24.04-arm)	8m 19s
ubuntu / clang-test (ubuntu-24.04)	8m 23s
ubuntu / clang-sanitizer-build (ubuntu-24.04)	1m 16s
ubuntu / gcc-test (ubuntu-24.04)	8m 21s
ubuntu / gcc-test (ubuntu-24.04-arm)	8m 13s
windows / clang-test	3m 9s
ubuntu / clang-sanitizer-test (ubuntu-24.04)	2m 51s
windows / msvc-test	4m 47s
windows / clang-test-extended	2m 56s
ubuntu / clang-sanitizer-test-extended (ubuntu-24.04)	2m 31s
windows / msvc-test-extended	2m 56s
ubuntu / clang-test-extended (ubuntu-24.04-arm)	4m 35s
ubuntu / clang-test-extended (ubuntu-24.04)	4m 31s
ubuntu / gcc-test-extended (ubuntu-24.04)	4m 31s
ubuntu / gcc-test-extended (ubuntu-24.04-arm)	4m 38s
ubuntu / gcc-build-codecov	5m 59s
mac / clang-test	4m 49s
mac / clang-test-extended	3m 2s
perf / macos-clang-build-perf-stats	1m 45s
perf / ubuntu-gcc-build-perf-stats	1m 43s
pages / build-scoreboard	16s
pages / build-doxygen-xml	25s
pages / build-sphinx	1m 54s
pages / deploy-pages	0s
	2h 7m 38s

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