Do not introduce timestamps in PNG files (for icons).
See <https://wiki.debian.org/ReproducibleBuilds/TimestampsInPNG>.

--- awesome-3.4.15/CMakeLists.txt	2013-02-11 14:50:21.000000000 +0100
+++ awesome-3.4.15/CMakeLists.txt	2016-06-16 13:59:30.528125439 +0200
@@ -295,7 +295,7 @@ macro(a_icon_convert match replacement i
         set(ALL_ICONS ${ALL_ICONS} ${output})
 
         add_custom_command(
-            COMMAND ${CONVERT_EXECUTABLE} ${input} -strip ${ARGN} ${output}
+            COMMAND ${CONVERT_EXECUTABLE} +set date:create +set date:modify -define png:exclude-chunk=time ${input} -strip ${ARGN} ${output}
             OUTPUT  ${output}
             DEPENDS ${input}
             VERBATIM)
'this.form.submit();'>
<option value='koszko' selected='selected'>koszko</option>
<option value='koszko-scripts'>koszko-scripts</option>
</select> <input type='submit' value='switch'/></form></td></tr>
<tr><td class='sub'>Wojtek's customized Guix</td><td class='sub right'></td></tr></table>
<table class='tabs'><tr><td>
<a href='/guix/about/'>about</a><a href='/guix/'>summary</a><a href='/guix/refs/?id=ab003b28c6e61575fc3f090374b9a67fe3d5c841'>refs</a><a class='active' href='/guix/log/nix/libstore/.gitignore'>log</a><a href='/guix/tree/nix/libstore/.gitignore?id=ab003b28c6e61575fc3f090374b9a67fe3d5c841'>tree</a><a href='/guix/commit/nix/libstore/.gitignore?id=ab003b28c6e61575fc3f090374b9a67fe3d5c841'>commit</a><a href='/guix/diff/nix/libstore/.gitignore?id=ab003b28c6e61575fc3f090374b9a67fe3d5c841'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/nix/libstore/.gitignore'>
<input type='hidden' name='id' value='ab003b28c6e61575fc3f090374b9a67fe3d5c841'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=ab003b28c6e61575fc3f090374b9a67fe3d5c841'>root</a>/<a href='/guix/log/nix?id=ab003b28c6e61575fc3f090374b9a67fe3d5c841'>nix</a>/<a href='/guix/log/nix/libstore?id=ab003b28c6e61575fc3f090374b9a67fe3d5c841'>libstore</a>/<a href='/guix/log/nix/libstore/.gitignore?id=ab003b28c6e61575fc3f090374b9a67fe3d5c841'>.gitignore</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/nix/libstore/.gitignore?id=ab003b28c6e61575fc3f090374b9a67fe3d5c841&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-06-24 19:55:22 +0100'>2020-06-24</span></td><td><a href='/guix/commit/nix/libstore/.gitignore?id=cd43b55da7ab51c996a7a3449c78f2a493616106'>nix: Tweak .gitignore files.</a><span class='msg-avail'>...<span class='msg-tooltip'>Remove .gitignore entries where they match source files that are tracked in
Git.  This is relevant to me at least, as some code searching tools use
.gitignore files and will ignore matched files.
</span></span></td><td>Christopher Baines</td></tr>