Disable -Werror=nonnull on getcwd(0, 4096) because GCC incorrectly warns that
the second argument should be NULL with recent glibc.  See:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96832
https://sourceware.org/bugzilla/show_bug.cgi?id=26545

diff --git a/nss/coreconf/nsinstall/nsinstall.c b/nss/coreconf/nsinstall/nsinstall.c
--- a/nss/coreconf/nsinstall/nsinstall.c
+++ b/nss/coreconf/nsinstall/nsinstall.c
@@ -236,14 +236,20 @@ main(int argc, char **argv)
 	return 0;
 
     if (!cwd) {
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wnonnull"
 	cwd = GETCWD(0, PATH_MAX);
+#pragma GCC diagnostic pop
 	if (!cwd)
 	    fail("could not get CWD");
     }
 
     /* make sure we can get into todir. */
     xchdir(todir);
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wnonnull"
     todir = GETCWD(0, PATH_MAX);
+#pragma GCC diagnostic pop
     if (!todir)
 	fail("could not get CWD in todir");
     tdlen = strlen(todir);
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<div class='path'>path: <a href='/guix/log/?id=92c4b7c0fd74b4e71ad70bd94211e4dba35a012f'>root</a>/<a href='/guix/log/gnu?id=92c4b7c0fd74b4e71ad70bd94211e4dba35a012f'>gnu</a>/<a href='/guix/log/gnu/packages?id=92c4b7c0fd74b4e71ad70bd94211e4dba35a012f'>packages</a>/<a href='/guix/log/gnu/packages/usb-modeswitch.scm?id=92c4b7c0fd74b4e71ad70bd94211e4dba35a012f'>usb-modeswitch.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/packages/usb-modeswitch.scm?id=92c4b7c0fd74b4e71ad70bd94211e4dba35a012f&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-01-20 08:57:24 +0000'>2020-01-20</span></td><td><a href='/guix/commit/gnu/packages/usb-modeswitch.scm?id=17fe068ed7372dbae09043885b8f091105bef143'>gnu: USB_ModeSwitch data: Update to 20191128.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/usb-modeswitch.scm (usb-modeswitch-data): Update to 20191128.
[source] Use HTTPS.
[home-page] Use HTTPS.
</span></span></td><td>Florian Pelz</td></tr>
<tr><td><span title='2020-01-20 08:57:17 +0000'>2020-01-20</span></td><td><a href='/guix/commit/gnu/packages/usb-modeswitch.scm?id=d0759f613480c13b8c81716eb46dc3606b3a34b0'>gnu: USB_ModeSwitch: Update to 2.6.0.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/usb-modeswitch.scm (usb-modeswitch): Update to 2.6.0.
[source]: Remove snippet that deletes jimtcl, which is no longer bundled.
Remove patch.  Use HTTPS.
[arguments]: Adapt to changed file names.
[home-page] Use HTTPS.
[license]: Fix missing BSD-2 license.
* gnu/packages/patches/usb-modeswitch-accept-config-arg.patch: Delete file.
* gnu/local.mk (dist_patch_DATA): Remove it.
</span></span></td><td>Florian Pelz</td></tr>