[PATCH STABLE V2] makefile: run Rust tests if cargo is installed

[Joerg Sonnenberger]

On Thu, Aug 22, 2019 at 02:57:04PM +0200, Raphaël Gomès wrote:
> diff -r 302dbc9d52be -r 450f65349bbe Makefile
> --- a/Makefile	Fri Aug 16 15:41:53 2019 +0300
> +++ b/Makefile	Wed Aug 21 17:56:50 2019 +0200
> @@ -16,6 +16,7 @@
>  export LC_ALL=C
>  TESTFLAGS ?= $(shell echo $$HGTESTFLAGS)
>  OSXVERSIONFLAGS ?= $(shell echo $$OSXVERSIONFLAGS)
> +CARGO=cargo
>  
>  # Set this to e.g. "mingw32" to use a non-default compiler.
>  COMPILER=

Please use ?= for CARGO too, makes it easier to override from the
command line.

Joerg