Fix build against libyaml 0.2.5.

Taken from upstream:
https://github.com/tlsa/libcyaml/commit/0e947264b947f51f7ea785068637c4bfce5d4171

diff --git a/test/units/save.c b/test/units/save.c
--- a/test/units/save.c
+++ b/test/units/save.c
@@ -3476,7 +3476,7 @@ static bool test_save_sequence_null_values_int(
 		ttest_report_ctx_t *report,
 		const cyaml_config_t *config)
 {
-	static const unsigned char ref[] =
+	static const unsigned char ref1[] =
 		"---\n"
 		"- 7\n"
 		"- 6\n"
@@ -3487,6 +3487,18 @@ static bool test_save_sequence_null_values_int(
 		"- \n"
 		"- 0\n"
 		"...\n";
+	/* As of libyaml 0.2.5, trailing spaces are not emitted. */
+	static const unsigned char ref2[] =
+		"---\n"
+		"- 7\n"
+		"- 6\n"
+		"- 5\n"
+		"-\n"
+		"- 3\n"
+		"- 2\n"
+		"-\n"
+		"- 0\n"
+		"...\n";
 	static const int d[] = { 7, 6, 5, 4, 3, 2, 1, 0 };
 	static const int *data[] = { d + 0, d + 1, d + 2, NULL,
 	                             d + 4, d + 5, NULL, d + 7, };
@@ -3515,11 +3527,12 @@ static bool test_save_sequence_null_values_int(
 		return ttest_fail(&tc, cyaml_strerror(err));
 	}
 
-	if (len != YAML_LEN(ref) || memcmp(ref, buffer, len) != 0) {
+	if ((len != YAML_LEN(ref1) || memcmp(ref1, buffer, len) != 0) &&
+	    (len != YAML_LEN(ref2) || memcmp(ref2, buffer, len) != 0)) {
 		return ttest_fail(&tc, "Bad data:\n"
 				"EXPECTED (%zu):\n\n%.*s\n\n"
 				"GOT (%zu):\n\n%.*s\n",
-				YAML_LEN(ref), YAML_LEN(ref), ref,
+				YAML_LEN(ref1), YAML_LEN(ref1), ref1,
 				len, len, buffer);
 	}
 
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<div class='path'>path: <a href='/guix/log/?id=9dea3f101f252331c049c03f501398a5ec837ba9'>root</a>/<a href='/guix/log/gnu?id=9dea3f101f252331c049c03f501398a5ec837ba9'>gnu</a>/<a href='/guix/log/gnu/packages?id=9dea3f101f252331c049c03f501398a5ec837ba9'>packages</a>/<a href='/guix/log/gnu/packages/squirrel.scm?id=9dea3f101f252331c049c03f501398a5ec837ba9'>squirrel.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/squirrel.scm?id=9dea3f101f252331c049c03f501398a5ec837ba9&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
23-02-16</span></td><td><a href='/guix/commit/gnu/packages/nfs.scm?id=672036c6dfe508810b565f4cf38e4f2aad2f7151'>gnu: Remove unneeded module imports.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/abiword.scm,
* gnu/packages/ada.scm,
* gnu/packages/agda.scm,
* gnu/packages/backup.scm,
* gnu/packages/barrier.scm,
* gnu/packages/bioinformatics.scm,
* gnu/packages/bootstrap.scm,
* gnu/packages/bqn.scm,
* gnu/packages/c.scm,
* gnu/packages/chemistry.scm,
* gnu/packages/coq.scm,
* gnu/packages/cross-base.scm,
* gnu/packages/databases.scm,
* gnu/packages/emacs-xyz.scm,
* gnu/packages/enlightenment.scm,
* gnu/packages/games.scm,
* gnu/packages/geo.scm,
* gnu/packages/ghostscript.scm,
* gnu/packages/gl.scm,
* gnu/packages/golang.scm,
* gnu/packages/jami.scm,
* gnu/packages/java-maths.scm,
* gnu/packages/kde-frameworks.scm,
* gnu/packages/kde-plasma.scm,
* gnu/packages/language.scm,
* gnu/packages/libreoffice.scm,
* gnu/packages/linphone.scm,
* gnu/packages/lisp.scm,
* gnu/packages/llvm.scm,
* gnu/packages/machine-learning.scm,
* gnu/packages/minetest.scm,
* gnu/packages/monitoring.scm,
* gnu/packages/nfs.scm,
* gnu/packages/ocr.scm,
* gnu/packages/opencl.scm,
* gnu/packages/pdf.scm,
* gnu/packages/python-xyz.scm,
* gnu/packages/racket.scm,
* gnu/packages/rust.scm,
* gnu/packages/syncthing.scm,
* gnu/packages/syndication.scm,
* gnu/packages/telegram.scm,
* gnu/packages/vulkan.scm,
* gnu/packages/web-browsers.scm,
* gnu/packages/web.scm,
* gnu/packages/webkit.scm: Remove some unecessary module imports.
</span></span></td><td>Efraim Flashner</td></tr>