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='2023-06-18 02:00:10 +0200'>2023-06-18</span></td><td><a href='/guix/commit/gnu/system/uuid.scm?id=65ed7a61f1ad01da440f0e7e08bfc32b43deed73'>uuid: Fix NTFS UUID stringification.</a><span class='msg-avail'>...<span class='msg-tooltip'>Previously, (ntfs-uuid-&gt;string (string-&gt;ntfs-uuid"5234ED0D34ECF53F"))
would yield "5234EDD34ECF53F".

Reported by sughosha in #guix.

* gnu/system/uuid.scm (ntfs-uuid-&gt;string): Pad hex bytes with zero when
needed.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2021-09-23 18:17:17 +0200'>2021-09-23</span></td><td><a href='/guix/commit/gnu/system/uuid.scm?id=90604348e14913da48327da05113d7da8ae7655a'>uuid: Support XFS.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/system/uuid.scm (string-&gt;xfs-uuid): New procedure.
(%uuid-parsers, %uuid-printers): Add ‘xfs’ file system type.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2020-11-07 13:40:46 +0100'>2020-11-07</span></td><td><a href='/guix/commit/gnu/system/uuid.scm?id=e87471dc510bc393e3306fba86f919dc6bf89b7b'>uuid: Add support for bcachefs.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/system/uuid.scm (string-&gt;bcachefs-uuid): New exported procedure.
(%uuid-parsers, %uuid-printers): Add the ‘bcachefs’ file system type.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2020-07-26 18:35:10 +0200'>2020-07-26</span></td><td><a href='/guix/commit/gnu/system/uuid.scm?id=675e56221e3dfc58cac94bf30835f16a9c41d530'>file-systems: Add NTFS support.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/system/uuid.scm (%ntfs-endianness): New macro,
(ntfs-uuid-&gt;string): new procedure,
(%ntfs-endianness): new variable,
(string-&gt;ntfs-uuid): new exported procedure,
(%uuid-parsers): add NTFS support,
(%uuid-printers): add NTFS support.
* gnu/build/file-systems.scm (%ntfs-endianness): New macro,
(ntfs-superblock?, read-ntfs-superblock, ntfs-superblock-uuid,
check-ntfs-file-system): new procedure,
(%partition-uuid-readers): add NTFS support,
(check-file-system): add NTFS support.
</span></span></td><td>Mathieu Othacehe</td></tr>