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;
tion>
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<div class='path'>path: <a href='/guix/log/?id=0be4d0947968168cacffe62e2a6fbfea9bee1683'>root</a>/<a href='/guix/log/tests?id=0be4d0947968168cacffe62e2a6fbfea9bee1683'>tests</a>/<a href='/guix/log/tests/monads.scm?id=0be4d0947968168cacffe62e2a6fbfea9bee1683'>monads.scm</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/monads.scm?id=0be4d0947968168cacffe62e2a6fbfea9bee1683&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2022-10-22 01:46:55 +0200'>2022-10-22</span></td><td><a href='/guix/commit/tests/monads.scm?id=a3619079f95213c4f983e69210ed12b38fd31022'>Remove now unnecessary uses of (guix grafts).</a><span class='msg-avail'>...<span class='msg-tooltip'>These modules would use (guix grafts) just to access '%graft?' and
related bindings, which are now in (guix store).

* gnu/ci.scm,
guix/gexp.scm,
guix/lint.scm,
guix/scripts.scm,
guix/scripts/archive.scm,
guix/scripts/build.scm,
guix/scripts/challenge.scm,
guix/scripts/deploy.scm,
guix/scripts/environment.scm,
guix/scripts/home.scm,
guix/scripts/pack.scm,
guix/scripts/package.scm,
guix/scripts/pull.scm,
guix/scripts/size.scm,
guix/scripts/system.scm,
guix/scripts/weather.scm,
tests/builders.scm,
tests/channels.scm,
tests/cpan.scm,
tests/derivations.scm,
tests/gexp.scm,
tests/graph.scm,
tests/guix-daemon.sh,
tests/monads.scm,
tests/pack.scm,
tests/packages.scm,
tests/profiles.scm,
tests/system.scm: Remove #:use-module (guix grafts).
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2022-07-10 23:57:14 +0200'>2022-07-10</span></td><td><a href='/guix/commit/tests/monads.scm?id=9fdc4b6c283c5aa5cf10205d87fb2c58b829b9d0'>monads: Add 'mparameterize'.</a><span class='msg-avail'>...<span class='msg-tooltip'>* etc/system-tests.scm (mparameterize): Move to...
* guix/monads.scm (mparameterize): ... here.
* tests/monads.scm ("mparameterize"): New test.
* .dir-locals.el (c-mode): Add it.
</span></span></td><td>Ludovic Courtès</td></tr>