[clang] [clang][SSAF] Optionally skip system-header contributors (PR #205446)

[Balázs Benics via cfe-commits]

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+// Regression for clang-reforge-7y4 / iter-03: end-to-end verification
+// of the --ssaf-no-extract-from-system-headers opt-out. Spec:
+// tu-summary-extraction's "System-header contributor opt-out flag"
+// requirement.
+
+// REQUIRES: system-darwin || system-linux
+
+// Setup: synthesise an -isystem header containing a benign user-named
+// symbol (no USR collision — that case is exercised end-to-end by the
+// parity-finale verification step against libJP2).
+// RUN: rm -rf %t.dir
+// RUN: mkdir -p %t.dir/sysinc
+// RUN: printf '#pragma clang system_header\nint *sys_gp; void sys_fn(int *p) { sys_gp = p; }\n' > %t.dir/sysinc/sys.h
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steakhal wrote:

I think we should use `split-file` like in similar SSAF tests to naturally spell the different files (including their newlines) in a single test specification file. Use `rm -rf ...` in the beginning to cleanup stale stuff, like in existing split-file tests.

https://github.com/llvm/llvm-project/pull/205446