gh-128779: Fix site venv() for system site-packages #139741

Job	Run time
Change detection / Compute changed files	10s
Check if generated files are up to date	4m 51s
Check if Autoconf files are up to date	27s
Docs	0s
Address sanitizer (ubuntu-24.04)	10m 3s
Ubuntu SSL tests with OpenSSL (ubuntu-24.04, 3.0.15)	2m 12s
Windows MSI${{ '' }}	0s
Ubuntu SSL tests with OpenSSL (ubuntu-24.04, 3.1.7)	2m 15s
Hypothesis tests on Ubuntu	8m 10s
Ubuntu SSL tests with OpenSSL (ubuntu-24.04, 3.2.3)	2m 16s
Ubuntu SSL tests with OpenSSL (ubuntu-24.04, 3.3.2)	2m 17s
Ubuntu SSL tests with OpenSSL (ubuntu-24.04, 3.4.0)	2m 20s
CIFuzz	0s
Thread sanitizer / Thread sanitizer	4m 48s
Thread sanitizer (free-threading) / Thread sanitizer	7m 26s
WASI / build and test	4m 16s
macOS (free-threading) / build and test (ghcr.io/cirruslabs/macos-runner:sonoma)	4m 14s
macOS / build and test (ghcr.io/cirruslabs/macos-runner:sonoma)	3m 48s
macOS / build and test (macos-13)	7m 37s
Ubuntu / build and test (ubuntu-24.04)	8m 34s
Ubuntu / build and test (ubuntu-24.04-arm)	6m 3s
Ubuntu (free-threading) / build and test (ubuntu-24.04)	11m 18s
Ubuntu (free-threading) / build and test (ubuntu-24.04-arm)	8m 4s
Ubuntu (bolt) / build and test (ubuntu-24.04)	12m 2s
Windows / build and test (arm64)	2m 58s
Windows (free-threading) / build and test (arm64)	2m 52s
Windows / build and test (Win32)	16m 17s
Windows / build and test (x64)	15m 8s
Windows (free-threading) / build and test (x64)	21m 47s
All required checks pass	1s
	2h 52m 14s

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