Without <limits.h>, INT_MAX is not defined.

diff --git a/transport.hxx b/transport.hxx
index 35a57a7..838add6 100644
--- a/transport.hxx
+++ b/transport.hxx
@@ -11,6 +11,7 @@
 #include <stdlib.h>
 #include <unistd.h>
 #include <string.h>
+#include <limits.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
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<div class='path'>path: <a href='/guix/log/?id=43c1952c978838f62b908fdbf4e304ad269eaeb6'>root</a>/<a href='/guix/log/tests?id=43c1952c978838f62b908fdbf4e304ad269eaeb6'>tests</a>/<a href='/guix/log/tests/guix-download.sh?id=43c1952c978838f62b908fdbf4e304ad269eaeb6'>guix-download.sh</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/guix-download.sh?id=43c1952c978838f62b908fdbf4e304ad269eaeb6&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-09-28 21:06:36 -0500'>2020-09-28</span></td><td><a href='/guix/commit/tests/guix-download.sh?id=d8934360d2453a403b5433e71d09188e4ed23b57'>tests: Simplify shell exit status negation;</a><span class='msg-avail'>...<span class='msg-tooltip'>* tests/guix-archive.sh, tests/guix-build-branch.sh, tests/guix-build.sh,
tests/guix-daemon.sh, tests/guix-download.sh, tests/guix-environment.sh,
tests/guix-gc.sh, tests/guix-git-authenticate.sh, tests/guix-graph.sh,
tests/guix-hash.sh, tests/guix-lint.sh, tests/guix-pack-relocatable.sh,
tests/guix-pack.sh, tests/guix-package-aliases.sh, tests/guix-package-net.sh,
tests/guix-package.sh: Use the shell '!' keyword to negate command exit status
in place of 'if ...; then false; else true; fi'
</span></span></td><td>Eric Bavier</td></tr>
<tr><td><span title='2017-08-20 20:55:45 +0800'>2017-08-20</span></td><td><a href='/guix/commit/tests/guix-download.sh?id=a02967d77af03d6468e25d6e26dbea0db919ce96'>guix download: Support retrieving local file without the URI scheme.</a><span class='msg-avail'>...<span class='msg-tooltip'>* guix/scripts/download.scm (guix-download): Treat the URL argument as a local
file path when it fails on 'string-&gt;uri'.  Call 'fetch' with the processed
'uri' instead of the original URL argument.
* tests/guix-download.sh: Adjust accordingly.
</span></span></td><td>宋文武</td></tr>