run-pass-valgrind tests don't actually run in valgrind

[sfackler]

compiletest requires the --valgrind-path parameter to be set or it treats run-pass-valgrind tests as normal run-pass tests. It doesn't appear that the build infrastructure ever actually sets this, though.

[jethrogb]

cc @aidanhs

[jyn514]

Mentoring instructions: Add the --valgrind-path arg somewhere around

rust/src/bootstrap/test.rs

Lines 1429 to 1435 in e9e0908

	// compiletest currently has... a lot of arguments, so let's just pass all
	// of them!
	cmd.arg("--compile-lib-path").arg(builder.rustc_libdir(compiler));
	cmd.arg("--run-lib-path").arg(builder.sysroot_libdir(compiler, target));
	cmd.arg("--rustc-path").arg(builder.rustc(compiler));

You may need to also install valgrind on the CI builders.

[jyn514]

Please also add --force-valgrind at the same time to avoid issues like this happening again (in fact maybe we should just remove that argument and have it on unconditionally?)