By default commands such as "ctest" would not look for certificates
at all: <https://issues.guix.gnu.org/issue/37371>.

This changes CMake such that commands honor SSL_CERT_FILE and SSL_CERT_DIR
as well as /etc/ssl/certs.

--- cmake-3.13.1/Source/cmCurl.cxx	2019-09-10 17:27:36.926907260 +0200
+++ cmake-3.13.1/Source/cmCurl.cxx	2019-09-10 17:52:35.475903919 +0200
@@ -2,11 +2,8 @@
    file Copyright.txt or https://cmake.org/licensing for details.  */
 #include "cmCurl.h"
 
-#if !defined(CMAKE_USE_SYSTEM_CURL) && !defined(_WIN32) &&                    \
-  !defined(__APPLE__) && !defined(CURL_CA_BUNDLE) && !defined(CURL_CA_PATH)
 #  define CMAKE_FIND_CAFILE
 #  include "cmSystemTools.h"
-#endif
 #include "cmStringAlgorithms.h"
 
 // curl versions before 7.21.5 did not provide this error code
@@ -30,6 +27,19 @@
     ::CURLcode res = ::curl_easy_setopt(curl, CURLOPT_CAINFO, cafile);
     check_curl_result(res, "Unable to set TLS/SSL Verify CAINFO: ");
   }
+
+  /* Honor the usual environment variables.  */
+  else if (cmSystemTools::GetEnv("SSL_CERT_FILE", e)) {
+    ::CURLcode res =
+      ::curl_easy_setopt(curl, CURLOPT_CAINFO, e.c_str());
+    check_curl_result(res, "Unable to set TLS/SSL Verify CAINFO: ");
+  }
+  else if (cmSystemTools::GetEnv("SSL_CERT_DIR", e)) {
+    ::CURLcode res =
+      ::curl_easy_setopt(curl, CURLOPT_CAPATH, e.c_str());
+    check_curl_result(res, "Unable to set TLS/SSL Verify CAINFO: ");
+  }
+
 #ifdef CMAKE_FIND_CAFILE
 #  define CMAKE_CAFILE_FEDORA "/etc/pki/tls/certs/ca-bundle.crt"
   else if (cmSystemTools::FileExists(CMAKE_CAFILE_FEDORA, true)) {
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</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=65ddb638fa105a47e0c0a1f5062dbecf8ab3af49'>root</a>/<a href='/guix/log/gnu?id=65ddb638fa105a47e0c0a1f5062dbecf8ab3af49'>gnu</a>/<a href='/guix/log/gnu/tests?id=65ddb638fa105a47e0c0a1f5062dbecf8ab3af49'>tests</a>/<a href='/guix/log/gnu/tests/vnstat.scm?id=65ddb638fa105a47e0c0a1f5062dbecf8ab3af49'>vnstat.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/tests/vnstat.scm?id=65ddb638fa105a47e0c0a1f5062dbecf8ab3af49&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2023-05-11 18:09:45 +0200'>2023-05-11</span></td><td><a href='/guix/commit/gnu/tests/vnstat.scm?id=d6f6b57766e95d2fa8af63d4460a2b303ca4d867'>tests: vnstat: Avoid call to 'getservbyname'.</a><span class='msg-avail'>...<span class='msg-tooltip'>This would break "make as-derivation" because /etc/services is
unavailable in the build environment:

  [ 38/ 80] loading...	 95.0% of 40 filesBacktrace:
  In guix/build/compile.scm:
      249:8 19 (compile-files "." "/gnu/store/s5nadqd6hkzivkxp33svwqslfn608ng5-guix-system-tests" ("gnu/tests/audio.scm" "gnu/tests/base.scm" "gnu/tests/ci.scm" "gnu/tests/cups.scm" "gnu/tests/d…" …) …)
  […]
  In unknown file:
	     0 (getserv "discard" "tcp")

  ERROR: In procedure getserv:
  In procedure getserv: no such service discard
  builder for `/gnu/store/…-guix-system-tests.drv' failed with exit code 1

* gnu/tests/vnstat.scm (run-vnstat-test): Hard-code 'guest-port' instead
of calling 'getservbyname'.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2023-05-11 16:38:29 +0200'>2023-05-11</span></td><td><a href='/guix/commit/gnu/tests/vnstat.scm?id=1e4c45b0dc1bc0bbfe064cedf22573ab70812562'>tests: Add vnstat tests.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/tests/vnstat.scm: New file.
* gnu/local.mk: Register it.

Signed-off-by: Ludovic Courtès &lt;ludo@gnu.org&gt;
</span></span></td><td>Bruno Victal</td></tr>