VTest2 (https://github.com/vtest/VTest2) was released and is a remplacement
for VTest. VTest was archived. So let's use the new version now.
If this commit is backported, the 2 following commits must also be
backported:
* 2808e3577 ("REGTESTS: Explicitly allow failing shell commands in some scripts")
* 82c291124 ("REGTESTS: Make the script testing conditional set-var compatible with Vtest2")
Build VTest temporarily from the sd-notify PR until the
https://github.com/vtest/VTest/pull/41 is merged.
This PR allows starting with -Ws in order to have more reliables tests
in master-worker mode.
On Linux, GNU make emits "w" at the beginning of the MAKEFLAGS
variable if -C is passed, which happens since vtest d6d228bcb3.
In fact it emits any of the command line flags without the leading
'-' in this case. gmake doesn't do that on BSD apparently. It's
documented under Options/Recursion in the GNU make doc. There's
also MFLAGS that could work but it does not contain the variables
definitions. So let's just avoid the -C that we don't really need.
This needs to be backported to stable versions.
