Support building for Android with NDK. (eProsima#269)

Treat Android as Linux.

Signed-off-by: Joel Cao <joel.cao@oppo.com>

Co-authored-by: Joel Cao <joel.cao@oppo.com>
Signed-off-by: Patrick Roncagliolo <ronca.pat@gmail.com>

CMakeLists.txt

@@ -136,7 +136,7 @@ endforeach()
 # Sources
 ###############################################################################
 # Check platform.
-if(CMAKE_SYSTEM_NAME STREQUAL "Linux")
+if(CMAKE_SYSTEM_NAME STREQUAL "Linux" OR CMAKE_SYSTEM_NAME STREQUAL "Android")
     set(UCLIENT_PLATFORM_LINUX ON)
 elseif(CMAKE_SYSTEM_NAME STREQUAL "Windows")
     set(UCLIENT_PLATFORM_WINDOWS ON)
@@ -325,7 +325,7 @@ if((CMAKE_SYSTEM_NAME STREQUAL "Windows") AND (UCLIENT_TARGET_TYPE STREQUAL "SHA
         )
 endif()
 
-if(CMAKE_SYSTEM_NAME STREQUAL "Linux")
+if(CMAKE_SYSTEM_NAME STREQUAL "Linux" OR CMAKE_SYSTEM_NAME STREQUAL "Android")
     find_package(Threads REQUIRED)
 endif()
 
@@ -590,4 +590,4 @@ if(BUILD_DOCUMENTATION)
         DESTINATION ${DOC_INSTALL_DIR}
         COMPONENT documentation
         )
-endif()
+endif()