The moc executable loops through headers on CPLUS_INCLUDE_PATH and stumbles
on the GCC internal _GLIBCXX_VISIBILITY macro.  Tell it to ignore it as it is
not supposed to be looking there to begin with.

Upstream report: https://bugreports.qt.io/browse/QTBUG-83160

diff --git a/src/tools/moc/main.cpp b/src/tools/moc/main.cpp
--- a/src/tools/moc/main.cpp
+++ b/src/tools/moc/main.cpp
@@ -188,6 +188,7 @@ int runMoc(int argc, char **argv)
     dummyVariadicFunctionMacro.arguments += Symbol(0, PP_IDENTIFIER, "__VA_ARGS__");
     pp.macros["__attribute__"] = dummyVariadicFunctionMacro;
     pp.macros["__declspec"] = dummyVariadicFunctionMacro;
+    pp.macros["_GLIBCXX_VISIBILITY"] = dummyVariadicFunctionMacro;
 
     QString filename;
     QString output;
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<div class='path'>path: <a href='/guix/log/?id=0a5b060be1e8966abc45e4782df83447510a90b4'>root</a>/<a href='/guix/log/tests?id=0a5b060be1e8966abc45e4782df83447510a90b4'>tests</a>/<a href='/guix/log/tests/guix-authenticate.sh?id=0a5b060be1e8966abc45e4782df83447510a90b4'>guix-authenticate.sh</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/tests/guix-authenticate.sh?id=0a5b060be1e8966abc45e4782df83447510a90b4&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2021-12-22 10:53:19 +0100'>2021-12-22</span></td><td><a href='/guix/commit/tests/guix-authenticate.sh?id=9ebc9ca070a21ba0aeb3f61202a8071bb250ccc8'>tests: Move keys into ./tests/keys/ and add a third ed25519 key.</a><span class='msg-avail'>...<span class='msg-tooltip'>The third key will be used in an upcoming commit.

Rename public keys to .pub.

* guix/tests/gnupg.scm (%ed25519-3-public-key-file): New variable.
(%ed25519-3-secret-key-file): New variable.
(%ed25519-2-public-key-file): Renamed from %ed25519bis-public-key-file.
(%ed25519-2-secret-key-file): Renamed from %ed25519bis-secret-key-file.
* tests/keys/ed25519-3.key: New file.
* tests/keys/ed25519-3.sec: New file.

Signed-off-by: Mathieu Othacehe &lt;othacehe@gnu.org&gt;
</span></span></td><td>Attila Lendvai</td></tr>