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='2023-10-04 15:09:26 +0200'>2023-10-04</span></td><td><a href='/guix/commit/gnu/packages/rdesktop.scm?id=264baefa881cf53d451bdfee3dcd6b2ade796d26'>gnu: freerdp: Update to 2.11.2.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/rdesktop.scm (freerdp): Update to 2.11.2.

Signed-off-by: Mathieu Othacehe &lt;othacehe@gnu.org&gt;
</span></span></td><td>Timotej Lazar</td></tr>
<tr><td><span title='2023-09-25 11:30:02 +0100'>2023-09-25</span></td><td><a href='/guix/commit/gnu/packages/rdesktop.scm?id=4aa2c04395ea489e874016a17ef2aff20b98cd32'>gnu: freerdp: Update to 2.11.1.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/rdesktop.scm (freerdp): Update to 2.11.1.
[inputs]: Add pcsc-lite.

Signed-off-by: Christopher Baines &lt;mail@cbaines.net&gt;
</span></span></td><td>Timotej Lazar</td></tr>
<tr><td><span title='2023-09-04 22:46:06 -0400'>2023-09-04</span></td><td><a href='/guix/commit/gnu/packages/rdesktop.scm?id=5a61bd462315ef530f7f8e76774aea8acbdb84d6'>gnu: freerdp: Enable server build.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/rdesktop.scm (freerdp): Enable server build.
[phases] (configure-flags): Enable server build flags.
[inputs]: Add server build dependencies and additional protocols
cairo, dbus, gsm, lame, libxdamage, opencl, openh264, openssl.

Signed-off-by: Maxim Cournoyer &lt;maxim.cournoyer@gmail.com&gt;
</span></span></td><td>Andy Tai</td></tr>
<tr><td><span title='2023-08-12 22:41:10 +0200'>2023-08-12</span></td><td><a href='/guix/commit/gnu/packages/rdesktop.scm?id=437a705f9cd288507d1bf77582d7a0cc5d1f56c3'>gnu: Add xorgxrdp.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/rdesktop.scm (xorgxrdp): New variable

Signed-off-by: Ludovic Courtès &lt;ludo@gnu.org&gt;
</span></span></td><td>Andy Tai</td></tr>
<tr><td><span title='2023-08-12 22:40:24 +0200'>2023-08-12</span></td><td><a href='/guix/commit/gnu/packages/rdesktop.scm?id=97377e389da711dfd0739a8cb41ba19aad90fa96'>gnu: Add xrdp.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/rdesktop.scm (xrdp): New variable

Signed-off-by: Ludovic Courtès &lt;ludo@gnu.org&gt;
</span></span></td><td>Andy Tai</td></tr>