Don't touch files in the srccache.

[maleadt]

Touching files in the srccache messes up out-of-tree builds when switching builds:

$ make -C build_a
$ make -C build_b
--> touches libuv files in srccache
$ make -C build_a
--> rebuilds libuv, and as a consequence all of julia

@vtjnash you added these commands as part of 217ce61, but are they still necessary? I couldn't trigger a run of autogen.

[vtjnash]

Yes, they're still necessary

[maleadt]

Could you elaborate? Any idea for alternative fixes? Having to rebuild that much when switching builddirs is somewhat annoying.