Mark zlib as found when using SAPI CMake build

Signed-off-by: Christian Blichmann <mail@blichmann.eu>
diff --git a/cmake/zlib/Download.cmake b/cmake/zlib/Download.cmake
index 126f3cd..24aad46 100644
--- a/cmake/zlib/Download.cmake
+++ b/cmake/zlib/Download.cmake
@@ -34,6 +34,7 @@
 
 set(_zlib_src "${CMAKE_BINARY_DIR}/zlib-src")
 
+set(ZLIB_FOUND TRUE)
 set(ZLIB_INCLUDE_DIRS ${_zlib_src})
 
 add_library(z STATIC
diff --git a/sandboxed_api/sandbox2/examples/zlib/CMakeLists.txt b/sandboxed_api/sandbox2/examples/zlib/CMakeLists.txt
index 6cd41ab..199a393 100644
--- a/sandboxed_api/sandbox2/examples/zlib/CMakeLists.txt
+++ b/sandboxed_api/sandbox2/examples/zlib/CMakeLists.txt
@@ -12,8 +12,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-find_package(ZLIB REQUIRED)
-
 # sandboxed_api/sandbox2/examples/zlib:zpipe_sandbox
 add_executable(sandbox2_zpipe_sandbox
   zpipe_sandbox.cc