fix #15631 (#15632)

* trigger valgrind failure on memory leak

* remove non-malloc tests

* remove ORC test

is redundant because we already have an ARC test

* only run valgrind tests on 64-bit Linux

* disable freebsd and openbsd

* Remove tleak_refc

As to not test implementation details (or bug)

* Fix test failures by removing redundant test

Since this tests/shoulfail/tvalgrind.nim was specified here to fail this test
itself fails since it will be skipped on non-linux CI

* Remove test, reason detailed in the previous commit

* Remove redundant disables

* Revert removing disables

* Add and use valgrind: leaks

* Fix

Co-authored-by: Clyybber <darkmine956@gmail.com>
Co-authored-by: n5m

tests/valgrind/tleak_arc.nim

@@ -0,0 +1,14 @@
+discard """
+valgrind: true
+cmd: "nim $target --gc:arc -d:useMalloc $options $file"
+exitcode: 1
+outputsub: "   definitely lost: 7 bytes in 2 blocks"
+disabled: "freebsd"
+disabled: "macosx"
+disabled: "openbsd"
+disabled: "windows"
+disabled: "32bit"
+"""
+
+discard alloc(3)
+discard alloc(4)