tests: add fork-f.test and vfork-f.test

Check how strace -f follows fork and vfork syscalls.

* tests/fork-f.c: New file.
* tests/fork-f.test: New test.
* tests/vfork-f.c: New file.
* tests/vfork-f.test: New test.
* tests/Makefile.am (check_PROGRAMS): Add fork-f and vfork-f.
(TESTS): Add fork-f.test and vfork-f.test.
* tests/.gitignore: Add fork-f and vfork-f.
diff --git a/tests/Makefile.am b/tests/Makefile.am
index c54fdf3..6c8f07c 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -56,6 +56,7 @@
 	fcntl64 \
 	file_handle \
 	filter-unavailable \
+	fork-f \
 	fstat \
 	fstat64 \
 	fstatat64 \
@@ -136,6 +137,7 @@
 	userfaultfd \
 	utime \
 	utimensat \
+	vfork-f \
 	wait \
 	xattr \
 	xet_robust_list \
@@ -184,6 +186,7 @@
 	fcntl64.test \
 	file_handle.test \
 	filter-unavailable.test \
+	fork-f.test \
 	fstat.test \
 	fstat64.test \
 	fstatat64.test \
@@ -260,6 +263,7 @@
 	userfaultfd.test \
 	utime.test \
 	utimensat.test \
+	vfork-f.test \
 	wait.test \
 	xattr.test \
 	xet_robust_list.test \