Remove build from test_command_generator

[arunks]

This is to remove the build command from scan. The test command builds and tests the UTs, adding a build command to this makes it redundant and increases execution times.

[KrauseFx]

There was a reason why the build command was there, this will need some additional trying if everything works as expected.

[mfurtak]

I don't have a good setup to test this right now, so I wonder if @ohwutup can provide feedback more quickly?

[ohayon]

hey @arunks! thanks for making this PR!

we have run some initial tests and are finding that while having the build step may appear redundant, that when xcodebuild is running the test command, it does not rebuild the scheme a second time, rather, it just builds the tests.

if you could, it would be great to see any logs that you may have that show the duplicated build that cause the lengthy run times of scan. either that, or if you have a test project that you could share we could do some deeper digging.

thanks!