[clang] [Modules] [HeaderSearch] Don't reenter headers if it is pragma once (PR #76119)

[via cfe-commits]

gulfemsavrun wrote:

This patch caused an lldb test to fail because of a missing import on Mac. 
```
FAIL: test_source_locations_from_objc_modules_dsym (TestExprDiagnostics.ExprDiagnosticsTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Volumes/Work/s/w/ir/x/w/llvm-llvm-project/lldb/packages/Python/lldbsuite/test/lldbtest.py", line 1707, in test_method
    return attrvalue(self)
           ^^^^^^^^^^^^^^^
  File "/Volumes/Work/s/w/ir/x/w/llvm-llvm-project/lldb/test/API/commands/expression/diagnostics/TestExprDiagnostics.py", line 175, in test_source_locations_from_objc_modules
    self.runCmd("expr @import Foundation")
  File "/Volumes/Work/s/w/ir/x/w/llvm-llvm-project/lldb/packages/Python/lldbsuite/test/lldbtest.py", line 2053, in runCmd
    self.assertTrue(self.res.Succeeded(), msg if (msg) else CMD_MSG(cmd))
AssertionError: False is not True : Command 'expr @import Foundation
Error output:
error: while importing modules:
While building module 'Foundation' imported from LLDBModulesMemoryBuffer:1:
While building module 'CoreFoundation' imported from /Volumes/Work/s/w/ir/cache/macos_sdk/XCode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX13.3.sdk/System/Library/Frameworks/Foundation.framework/Headers/Foundation.h:6:
While building module 'std' imported from /Volumes/Work/s/w/ir/cache/macos_sdk/XCode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX13.3.sdk/System/Library/Frameworks/CoreFoundation.framework/Headers/CoreFoundation.h:19:
In file included from <module-includes>:34:
In file included from /Volumes/Work/s/w/ir/cache/macos_sdk/XCode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX13.3.sdk/usr/include/c++/v1/complex.h:28:
In file included from /Volumes/Work/s/w/ir/cache/macos_sdk/XCode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX13.3.sdk/usr/include/c++/v1/ccomplex:21:
In file included from /Volumes/Work/s/w/ir/cache/macos_sdk/XCode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX13.3.sdk/usr/include/c++/v1/complex:243:
In file included from /Volumes/Work/s/w/ir/cache/macos_sdk/XCode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX13.3.sdk/usr/include/c++/v1/sstream:186:
In file included from /Volumes/Work/s/w/ir/cache/macos_sdk/XCode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX13.3.sdk/usr/include/c++/v1/istream:163:
In file included from /Volumes/Work/s/w/ir/cache/macos_sdk/XCode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX13.3.sdk/usr/include/c++/v1/__iterator/istreambuf_iterator.h:15:
/Volumes/Work/s/w/ir/cache/macos_sdk/XCode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX13.3.sdk/usr/include/c++/v1/__iterator/iterator.h:22:56: reference to unresolved using declaration
   22 | template<class _Category, class _Tp, class _Distance = ptrdiff_t,
      |                                                        ^

/Volumes/Work/s/w/ir/cache/macos_sdk/XCode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX13.3.sdk/usr/include/c++/v1/cstddef:51:1: note: using declaration annotated with 'using_if_exists' here
   51 | using ::ptrdiff_t _LIBCPP_USING_IF_EXISTS;
      | ^
```

https://logs.chromium.org/logs/fuchsia/buildbucket/cr-buildbucket/8758053465398947297/+/u/lldb/test/stdout

https://github.com/llvm/llvm-project/pull/76119