test-online-cpus: helper to return cpu count

Created helper executable to print the value of online_cpus()
allowing multi-threaded tests to be skipped when appropriate.
Signed-off-by: NJeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Makefile

@@ -619,6 +619,7 @@ TEST_PROGRAMS_NEED_X += test-line-buffer
 TEST_PROGRAMS_NEED_X += test-match-trees
 TEST_PROGRAMS_NEED_X += test-mergesort
 TEST_PROGRAMS_NEED_X += test-mktemp
+TEST_PROGRAMS_NEED_X += test-online-cpus
 TEST_PROGRAMS_NEED_X += test-parse-options
 TEST_PROGRAMS_NEED_X += test-path-utils
 TEST_PROGRAMS_NEED_X += test-prio-queue

t/helper/.gitignore

@@ -16,6 +16,7 @@
 /test-match-trees
 /test-mergesort
 /test-mktemp
+/test-online-cpus
 /test-parse-options
 /test-path-utils
 /test-prio-queue

t/helper/test-online-cpus.c

+#include "git-compat-util.h"
+#include "thread-utils.h"
+
+int cmd_main(int argc, const char **argv)
+{
+	printf("%d\n", online_cpus());
+	return 0;
+}