Add CMake support

Change-Id: I716e1fa3ec43bfe57326f5a691131505f84b7832

cpp/platform/impl/default/CMakeLists.txt

@@ -0,0 +1,53 @@
+add_library(platform_impl_default STATIC)
+
+target_sources(platform_impl_default
+  PRIVATE
+    default_condition_variable.cc
+    default_lock.cc
+    default_platform.cc
+  PUBLIC
+    default_condition_variable.h
+    default_lock.h
+    default_platform.h
+)
+
+target_include_directories(platform_impl_default
+  PUBLIC
+    ${CMAKE_CURRENT_SOURCE_DIR}
+)
+
+target_link_libraries(platform_impl_default
+  PUBLIC
+    platform_api
+    platform_types
+)
+
+add_library(platform_impl_default_lock STATIC)
+
+target_sources(platform_impl_default_lock
+  PRIVATE
+    default_lock.cc
+  PUBLIC
+    default_lock.h
+)
+
+target_link_libraries(platform_impl_default_lock
+  PUBLIC
+    platform_api
+)
+
+add_library(platform_impl_default_cond_var STATIC)
+
+target_sources(platform_impl_default_cond_var
+  PRIVATE
+    default_condition_variable.cc
+  PUBLIC
+    default_condition_variable.h
+)
+
+target_link_libraries(platform_impl_default_cond_var
+  PUBLIC
+    platform_api
+    platform_impl_default_lock
+    platform_types
+)

cpp/platform/impl/sample/CMakeLists.txt

@@ -0,0 +1,18 @@
+add_library(platform_impl_sample STATIC)
+
+target_sources(platform_impl_sample
+  PRIVATE
+    sample_wifi_medium.cc
+  PUBLIC
+    sample_platform.h
+    sample_wifi_medium.h
+)
+
+target_link_libraries(platform_impl_sample
+  PUBLIC
+    absl::time
+    platform_api
+    platform_port_string
+    platform_types
+    platform_utils
+)