Abseil insists on having a Google Test directory, even if we're not going to
run (or even build) the tests.
This changes forces all test settings to `OFF` just for Abseil, allowing
SAPI builds to complete normally. Embedding projects should not be affected,
if they already included Abseil.
PiperOrigin-RevId: 309035680
Change-Id: Ie46297d8b502d92d0c10ef04360e992bcee4964b
This change moves away from a classical superbuild which downloads and builds
at build time. Instead, we now follow a "Fetch Content" workflow (available as
FetchContent in CMake 3.11+) and download dependencies at config time.
Rationale: Superbuild projects have the disadvantage that projects cannot
directly access their individual declared targets. This is not a problem with
regular libraries, as those are usually/supposed to be installed. With
Sandboxed API, this is not desirable, as it has dependencies like Abseil and
glog, which are almost always consumed by including their source tree using
add_subdirectory().
Fixes#10 and makes external embedding easier.
PiperOrigin-RevId: 260129870
Change-Id: I70f295f29a6e4fc8c330512c94b01ef10c017166
