CMake: require libjpeg-turbo, not libjpeg

cmake/CMakeLists.txt

 # Boilerplate.
 cmake_minimum_required (VERSION 3.1)   # First version with CMAKE_CXX_STANDARD.
 project (skimake)
 set (CMAKE_CXX_STANDARD 11)
 
 # Default to Release mode.  We're mainly targeting Skia users, not Skia developers.
 if (NOT CMAKE_BUILD_TYPE)
     set (CMAKE_BUILD_TYPE Release)
 endif ()
 
@@ skipping 129 matching lines @@
     set_source_files_properties(${sse42_srcs} PROPERTIES COMPILE_FLAGS -msse4.2)
     set_source_files_properties(${avx_srcs}   PROPERTIES COMPILE_FLAGS -mavx)
     set_source_files_properties(${avx2_srcs}  PROPERTIES COMPILE_FLAGS -mavx2)
 endif()
 
 # Detect our optional dependencies.
 # If we can't find them, don't build the parts of Skia that use them.
 find_package (EXPAT)
 find_package (Lua)
 find_package (ZLIB)
-# No find_package for libwebp as far as I can tell, so simulate it here.
+
+# For libraries that don't have find_package() scripts, we do it ourselves:
 find_path (WEBP_INCLUDE_DIRS "webp/decode.h")
-find_library (WEBP_LIBRARIES webp)
+find_library (WEBP_LIBRARIES "webp")
+
 find_path (OSMESA_INCLUDE_DIRS "GL/osmesa.h")
 find_library(OSMESA_LIBRARIES "OSMesa")
 
 if (UNIX AND NOT APPLE)
     find_package (Freetype)
-    # Same deal for fontconfig.
+    find_package (GIF)
+
     find_path (FONTCONFIG_INCLUDE_DIRS "fontconfig/fontconfig.h")
     find_library (FONTCONFIG_LIBRARIES fontconfig)
-    find_package (GIF)
-    find_package (JPEG)
+
+    # We require libjpeg-turbo >= 1.5.0.
+    find_package(PkgConfig)
+    pkg_check_modules(JPEG_TURBO libjpeg>=1.5.0)
 endif()
 
 # Do not compile SkRawCodec.
 remove_srcs(../src/codec/*Raw*.cpp)
 
 # TODO: macro away this if (found) ... else() ... endif() stuff.
 
 if (EXPAT_FOUND)
     list (APPEND private_includes ${EXPAT_INCLUDE_DIRS})
     list (APPEND libs             ${EXPAT_LIBRARIES})
 else()
     remove_srcs (../src/ports/SkFontMgr_android_parser.cpp)
 endif()
 
 if (GIF_FOUND)
     list (APPEND private_includes ${GIF_INCLUDE_DIRS})
     list (APPEND libs             ${GIF_LIBRARIES})
     add_definitions(-DSK_HAS_GIF_LIBRARY)
 else()
     remove_srcs(../src/images/*GIF*)
     remove_srcs(../src/codec/*Gif*)
 endif()
 
-if (JPEG_FOUND)
-    list (APPEND private_includes ${JPEG_INCLUDE_DIRS})
-    list (APPEND libs             ${JPEG_LIBRARIES})
+if (JPEG_TURBO_FOUND)
+    list (APPEND private_includes ${JPEG_TURBO_INCLUDE_DIRS})
+    list (APPEND libs             ${JPEG_TURBO_LIBRARIES})
     add_definitions(-DSK_HAS_JPEG_LIBRARY)
 else()
     remove_srcs(../src/images/*JPEG*)
     remove_srcs(../src/codec/*Jpeg*)
 endif()
 
 if (LUA_FOUND)
     list (APPEND private_includes ${LUA_INCLUDE_DIR})
     list (APPEND libs             ${LUA_LIBRARIES})
 else()
@@ skipping 152 matching lines @@
         file (APPEND ${skia_h_path} "#include \"${filename_component}\"\n")
       endif ()
     endforeach()
   endif()
 endforeach()
 file(APPEND ${skia_h_path} "\n#endif  // skia_DEFINED\n")
 
 # Now build a simple example app that uses Skia via libskia.so.
 add_executable(example example.cpp)
 target_link_libraries(example skia ${OPENGL_LIBRARIES})