Without this patch, the 'make install' attempts to 'install' a directory, which causes an error.

diff --git a/c++/src/build-system/Makefile.in.top b/c++/src/build-system/Makefile.in.top
index 1abe44f..d6000b3 100644
--- a/c++/src/build-system/Makefile.in.top
+++ b/c++/src/build-system/Makefile.in.top
@@ -51,7 +51,7 @@ install-toolkit:
 	    done
 	cd $(includedir0) && find * -name CVS -prune -o -print |\
             cpio -pd $(pincludedir)
-	$(INSTALL) -m 644 $(incdir)/* $(pincludedir)
+	cp -R $(incdir)/* $(pincludedir)
 ## set up appropriate build and status directories somewhere under $(libdir)?
 
 install-gbench:
 type='hidden' name='id' value='8ba50751922be3ed88d9ec9192a21654f66ff8df'/><select name='h' onchange='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=8ba50751922be3ed88d9ec9192a21654f66ff8df'>refs</a><a class='active' href='/guix/log/gnu/system/linux-container.scm'>log</a><a href='/guix/tree/gnu/system/linux-container.scm?id=8ba50751922be3ed88d9ec9192a21654f66ff8df'>tree</a><a href='/guix/commit/gnu/system/linux-container.scm?id=8ba50751922be3ed88d9ec9192a21654f66ff8df'>commit</a><a href='/guix/diff/gnu/system/linux-container.scm?id=8ba50751922be3ed88d9ec9192a21654f66ff8df'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/gnu/system/linux-container.scm'>
<input type='hidden' name='id' value='8ba50751922be3ed88d9ec9192a21654f66ff8df'/><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=8ba50751922be3ed88d9ec9192a21654f66ff8df'>root</a>/<a href='/guix/log/gnu?id=8ba50751922be3ed88d9ec9192a21654f66ff8df'>gnu</a>/<a href='/guix/log/gnu/system?id=8ba50751922be3ed88d9ec9192a21654f66ff8df'>system</a>/<a href='/guix/log/gnu/system/linux-container.scm?id=8ba50751922be3ed88d9ec9192a21654f66ff8df'>linux-container.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/gnu/system/linux-container.scm?id=8ba50751922be3ed88d9ec9192a21654f66ff8df&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2022-08-09 20:32:13 +0200'>2022-08-09</span></td><td><a href='/guix/commit/gnu/system/linux-container.scm?id=26af06b66b65354a46b2196d1c11c90168b7fa12'>linux-container: container-script: Parse command line options.</a><span class='msg-avail'>...</span></td><td>Ricardo Wurmus</td></tr>
<tr><td><span title='2022-05-31 14:53:42 -0400'>2022-05-31</span></td><td><a href='/guix/commit/gnu/system/linux-container.scm?id=edac21bfc78ffea85f4dac7206e5e7cd621bba19'>gnu: Remove wicd.</a><span class='msg-avail'>...</span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2022-03-19 18:26:00 +0100'>2022-03-19</span></td><td><a href='/guix/commit/gnu/system/linux-container.scm?id=cff9fee82a06f58b10a5b3a7743295c53f7988b8'>linux-container: Add #:guest-uid and #:guest-gid to 'eval/container'.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2022-03-19 18:26:00 +0100'>2022-03-19</span></td><td><a href='/guix/commit/gnu/system/linux-container.scm?id=c77544b387882450599b5f7e2712abdadaa074e9'>linux-container: 'eval/container' honors #:namespaces.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-01-13 22:24:18 +0100'>2021-01-13</span></td><td><a href='/guix/commit/gnu/system/linux-container.scm?id=0d22fc8d36e4efba9748c94cab7cedbbe2bbb5bf'>services: shepherd: 'shepherd-service-type' requires documentation.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-10-01 09:27:33 +0200'>2020-10-01</span></td><td><a href='/guix/commit/gnu/system/linux-container.scm?id=5627bfe45ce46f498979b4ad2deab1fdfed22b6c'>Instantiate nscd in each system container.</a><span class='msg-avail'>...</span></td><td>Jason Conroy</td></tr>
<tr><td><span title='2020-04-26 22:49:49 +0200'>2020-04-26</span></td><td><a href='/guix/commit/gnu/system/linux-container.scm?id=0e5c2d5e145118ec47329d6b3a534344d2e89cd3'>services: system: Initial entries are non-monadic.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>