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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packages/patches/calibre-no-updates-dialog.patch?id=5d53eec337fb410d1d1c0b89ce3dd29a8edf9e49'>gnu: calibre: Update to 5.14.0.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/ebook.scm (calibre): Update to 5.14.0.
[source]: Adjust the snippet to preserve some files used by the HTML reader.
[native-inputs]: Add python-pyqt-builder. Replace python2-flake8 with
python-flake8.
[inputs]: Remove chmlib, js-mathjax, python-chardet, and python-sip.  Add
python-cchardet, python-speechd, python-zeroconf, python-py7zr, python-pychm,
python-pycryptodome, libjpeg, and libjxr.  Replace all Python 2 dependencies
with their Python 3 equivalents.
[arguments]: Build with the default Python and adjust custom phases accordingly.
Adjust the 'configure' phase to changes in how Calibre uses SIP, and patch
lookup paths for libjpeg and libjxr.
Rename the 'build-extra' phase to 'install-rapydscript', and run it after the
'install' phase. Adjust it for Calibre 5.14.0.
* gnu/packages/patches/calibre-no-updates-dialog.patch,
gnu/packages/patches/calibre-remove-test-sqlite.patch,
gnu/packages/patches/calibre-remove-test-unrar.patch: Adjust patches for Calibre
5.14.0.
</span></span></td><td>Brendan Tildesley</td></tr>