These tests rely on changing the definition of the "libc" module which
is a default module provided by the cc.GatherRequiredDepsForTest()
function. That function is called from within testApexContext() and so
added by default.
Previously, the tests relied on a number of factors to work:
1. All the default cc modules were added to the bp contents that were
passed to testApexContext().
2. testApexContext() passed the augmented bp contents to
TestArchConfig().
3. TestArchConfig() only stored the supplied bp contents in the root
Android.bp file if it did not exist.
So, in order to override the default modules it simply made sure to add
its own Android.bp file into the file system first.
Unfortunately, that does not work with the test fixtures as the default
modules are defined in their own specific paths to avoid conflicting
with each other. To achieve the same effect as previously, i.e. no
default modules, this test uses an emptyFixtureFactory and only adds
preparers for cc and apex build components and ignores the default
module definitions altogether.
Bug: 181070625
Test: m nothing
Change-Id: Ic6b961dd2bd78c32cb326b2c7905426ee971c2d8
a02cae345b