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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<tr><td><span title='2023-09-25 11:30:02 +0100'>2023-09-25</span></td><td><a href='/guix/commit/gnu/packages/patches/kiwix-desktop-newer-libkiwix.patch?id=d953a1e5d678be58887704df6f10cb19a8fd48bf'>gnu: kiwix-desktop: Update to 2.3.1.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/web.scm (kiwix-desktop): Update to 2.3.1.
* gnu/packages/patches/kiwix-desktop-newer-libkiwix.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.

Signed-off-by: Denis 'GNUtoo' Carikli &lt;GNUtoo@cyberdimension.org&gt;
Signed-off-by: Christopher Baines &lt;mail@cbaines.net&gt;
</span></span></td><td>Denis 'GNUtoo' Carikli</td></tr>