H2ws creation refactor: moved function to build binary, so that it's built only if websockets tests are run

[PaulLodge]

Moved the h2ws build, so that it's built only if the websockets tests are run, so that if they aren't needed the ts won't keep trying to build them for each test that is run, thereby removing the need to to have all the dependencies even though the tests are never run.

[notroj]

It is weird that this stuff is built during the test run rather than during build... have you looked at moving it out?

[PaulLodge]

@notroj thanks
The reasoning behind the building the various test binaries (h2ws, mod_aptest, mod_h1test and mod_h2test), makes sense when the tests are run; now with the recent major shift towards using the python TS, it makes more sense to move them out and to build them when httpd is built, which would avoid the overhead for each test.

[PaulLodge]

This the #784 that add the above mentioned functionality that moves the test binary build to the httpd build phase instead of during the test run itself.

I'm still sat on the fence as to whether to keep this one too as it does make sense if the binary in this case h2ws isn't created at build time.