runtime: TestStackMem needs to be run in isolation to be accurate

[randall77]

See CL 119330044

TestStackMem measures the amount of stack used, which can change due to other tests
running simultaneously.

We see instances of the amount of stack used going negative.  This bug requests a way of
running this test in isolation so it isn't degraded by other nearby tests.

[dvyukov]

Comment 1:

We have crash_test.go:executeTest for this. It runs a program in complete isolation.

[ianlancetaylor]

Comment 2:

Labels changed: added repo-main, release-go1.4.

[rsc]

Comment 3:

Other tests do not run simultaneously by default. This is more likely an accounting
error, probably fixed by now.

[rsc]

Comment 4:

Labels changed: added release-none, removed release-go1.4.

Owner changed to @randall77.

Status changed to Accepted.