Speed up VS2017 Appveyor which is taking 45 mins

VS2013 was taking ~33 mins.

Some of this may be some timeouts. Some may be a slower compiler?

Build and test times:

$ egrep 'Build dire|Test project' Downloads/log\ \(22\).txt 
[00:02:01]    Build directory: C:/projects/dynamorio/build/build_debug-internal-32
[00:06:48] Test project C:/projects/dynamorio/build/build_debug-internal-32
[00:21:01]    Build directory: C:/projects/dynamorio/build/build_debug-internal-64
[00:25:34] Test project C:/projects/dynamorio/build/build_debug-internal-64
[00:35:33]    Build directory: C:/projects/dynamorio/build/build_release-external-32
[00:38:12] Test project C:/projects/dynamorio/build/build_release-external-32
[00:38:12]    Build directory: C:/projects/dynamorio/build/build_release-external-64
[00:44:47] Test project C:/projects/dynamorio/build/build_release-external-64
[00:44:47]    Build directory: C:/projects/dynamorio/build/build_release-external-64
[00:44:47] Command exited with code 1

We can probably shrink some of the longer tests: like drcachesim tests running that concurrency app and taking a minute each.