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)?
 
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<div class='path'>path: <a href='/guix/log/?id=61576d592714610d77200a56e154784a5c8b051e'>root</a>/<a href='/guix/log/tests?id=61576d592714610d77200a56e154784a5c8b051e'>tests</a>/<a href='/guix/log/tests/bournish.scm?id=61576d592714610d77200a56e154784a5c8b051e'>bournish.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/bournish.scm?id=61576d592714610d77200a56e154784a5c8b051e&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
sage (<a href='/guix/log/po/doc/guix-manual.zh_CN.po?id=d3d00b1b4f2875675999919fa7e892c36bfff4c6&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2022-06-04 17:42:54 +0200'>2022-06-04</span></td><td><a href='/guix/commit/po/doc/guix-manual.zh_CN.po?id=809c57c872a6dd48007d1abf6d7f3dd1482ec53a'>nls: Update translations.</a><span class='msg-avail'>...</span></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2022-05-01 18:07:34 +0200'>2022-05-01</span></td><td><a href='/guix/commit/po/doc/guix-manual.zh_CN.po?id=6b4124cdcc203d47dc40158062afa1497d73d592'>nls: Update translations.</a><span class='msg-avail'>...</span></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2022-04-02 18:42:36 +0200'>2022-04-02</span></td><td><a href='/guix/commit/po/doc/guix-manual.zh_CN.po?id=8a208df17fe81fbf34f5a86cc52bb0b8e33c7b96'>nls: Update translations.</a><span class='msg-avail'>...</span></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2022-03-01 22:17:18 +0100'>2022-03-01</span></td><td><a href='/guix/commit/po/doc/guix-manual.zh_CN.po?id=8c92d85e06e65c5cdb5f6c75faf8aa33e5a68513'>nls: Update translations.</a><span class='msg-avail'>...</span></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2022-02-04 18:29:00 +0100'>2022-02-04</span></td><td><a href='/guix/commit/po/doc/guix-manual.zh_CN.po?id=8391a99d089322a39cbacb1e6dc2979d8b2ef7c9'>nls: Update translations.</a><span class='msg-avail'>...</span></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2022-01-09 11:35:59 +0100'>2022-01-09</span></td><td><a href='/guix/commit/po/doc/guix-manual.zh_CN.po?id=934b0cdfee2078bad42429427e12d6ee2ddb7fec'>nls: Update translations.</a><span class='msg-avail'>...</span></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2021-12-04 19:40:52 +0100'>2021-12-04</span></td><td><a href='/guix/commit/po/doc/guix-manual.zh_CN.po?id=7fcb20a8fa242ab53b9bc97ef0b0367c6a399bd4'>nls: Update translations.</a></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2021-11-06 14:06:36 +0100'>2021-11-06</span></td><td><a href='/guix/commit/po/doc/guix-manual.zh_CN.po?id=85430a9ea6f32aaae3e34741e292a01a2de62ee0'>nls: Update translations.</a><span class='msg-avail'>...</span></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2021-10-17 22:10:25 +0200'>2021-10-17</span></td><td><a href='/guix/commit/po/doc/guix-manual.zh_CN.po?id=15c91189cb61c579f4289047c79530cefe75215f'>nls: Update translations.</a></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2021-09-02 04:06:52 +0200'>2021-09-02</span></td><td><a href='/guix/commit/po/doc/guix-manual.zh_CN.po?id=1ff2092a39dc5c7c7cd9b4a0ba4b59f92e738efc'>nls: Update translations.</a><span class='msg-avail'>...</span></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2021-08-04 14:49:53 +0200'>2021-08-04</span></td><td><a href='/guix/commit/po/doc/guix-manual.zh_CN.po?id=6c10c96fedf707d7be059aeb79bd5c8e2d2fa210'>nls: Update translations.</a><span class='msg-avail'>...</span></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2021-05-10 22:34:43 -0400'>2021-05-10</span></td><td><a href='/guix/commit/po/doc/guix-manual.zh_CN.po?id=21fcced608c93e1ac836cdd9ab8c5d200c667e75'>nls: Update translations.</a></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2021-04-18 13:18:02 +0200'>2021-04-18</span></td><td><a href='/guix/commit/po/doc/guix-manual.zh_CN.po?id=5d1f110b454b9de30a8dde8d51a213bb956d54f3'>nls: Update 'zh_CN' translations.</a></td><td>Julien Lepiller</td></tr>