fix(v8): restore Linux sandbox artifact builds

Keep non-Windows rusty-v8 consumers on the resolved 147.4.0 source-built graph. Avoid mixing LLVM's default libc++ headers into rusty-v8's custom libc++ build, propagate that configuration to external C++ deps, and export the musl-specific libc++ define through the shared header target.

Also make checksum validation follow the remaining prebuilt asset version while the source-build migration is in progress.

Co-authored-by: Codex <noreply@openai.com>

.github/scripts/rusty_v8_module_bazel.py

@@ -9,6 +9,7 @@ from pathlib import Path
 
 SHA256_RE = re.compile(r"[0-9a-f]{64}")
 HTTP_FILE_BLOCK_RE = re.compile(r"(?ms)^http_file\(\n.*?^\)\n?")
+HTTP_FILE_VERSION_RE = re.compile(r"^rusty_v8_([0-9]+)_([0-9]+)_([0-9]+)_")
 
 
 class RustyV8ChecksumError(ValueError):
@@ -95,6 +96,18 @@ def rusty_v8_http_files(module_bazel: str, version: str) -> list[RustyV8HttpFile
     return entries
 
 
+def rusty_v8_http_file_versions(module_bazel: str) -> list[str]:
+    versions = set()
+    for match in HTTP_FILE_BLOCK_RE.finditer(module_bazel):
+        name = string_field(match.group(0), "name")
+        if not name:
+            continue
+        version_match = HTTP_FILE_VERSION_RE.match(name)
+        if version_match:
+            versions.add(".".join(version_match.groups()))
+    return sorted(versions)
+
+
 def module_entry_set_errors(
     entries: list[RustyV8HttpFile],
     checksums: dict[str, str],