added CMakeLists.txt for build WebP

3rdparty/libwebp/CMakeLists.txt

+# ----------------------------------------------------------------------------
+#  CMake file for libwebp. See root CMakeLists.txt
+#
+# ----------------------------------------------------------------------------
+project(${WEBP_LIBRARY})
+
+ocv_include_directories(${CMAKE_CURRENT_SOURCE_DIR})
+ocv_include_directories("${CMAKE_CURRENT_SOURCE_DIR}/cpu-features")
+
+file(GLOB lib_srcs dec/*.c dsp/*.c enc/*.c mux/*.c utils/*.c webp/*.c)
+file(GLOB lib_hdrs dec/*.h dsp/*.h enc/*.h mux/*.h utils/*.h webp/*.h)
+
+if(ANDROID AND ARMEABI_V7A AND NOT NEON)
+  foreach(file ${lib_srcs})
+    if("${file}" MATCHES "_neon.c")
+      set_source_files_properties("${file}" COMPILE_FLAGS "-mfpu=neon")
+    endif()
+  endforeach()
+endif()
+
+file(GLOB cpuf_s cpu-features/*.c)
+file(GLOB cpuf_h cpu-features/*.h)
+
+if(ANDROID)
+  set(lib_srcs ${lib_srcs} ${cpuf_s})
+  set(lib_hdrs ${lib_hdrs} ${cpuf_h})
+endif()
+
+# ----------------------------------------------------------------------------------
+#         Define the library target:
+# ----------------------------------------------------------------------------------
+
+add_definitions(-DWEBP_USE_THREAD)
+
+add_library(${WEBP_LIBRARY} STATIC ${lib_srcs} ${lib_hdrs})
+
+if(UNIX)
+  if(CMAKE_COMPILER_IS_GNUCXX OR CV_ICC)
+    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fPIC")
+  endif()
+endif()
+
+ocv_warnings_disable(CMAKE_C_FLAGS -Wunused-variable -Wshadow)
+
+set_target_properties(${WEBP_LIBRARY}
+  PROPERTIES OUTPUT_NAME ${WEBP_LIBRARY}
+  DEBUG_POSTFIX "${OPENCV_DEBUG_POSTFIX}"
+  ARCHIVE_OUTPUT_DIRECTORY ${3P_LIBRARY_OUTPUT_PATH}
+  )
+
+if(ENABLE_SOLUTION_FOLDERS)
+  set_target_properties(${WEBP_LIBRARY} PROPERTIES FOLDER "3rdparty")
+endif()
+
+if(NOT BUILD_SHARED_LIBS)
+  install(TARGETS ${WEBP_LIBRARY} ARCHIVE DESTINATION ${OPENCV_3P_LIB_INSTALL_PATH} COMPONENT main)
+endif()