Make deps: Use own nasm for ffmpeg and x264

Fixes the warning: building for macOS, but linking in object file

Differential Revision: https://developer.blender.org/D8235

build_files/build_environment/cmake/ffmpeg.cmake

@@ -50,7 +50,8 @@ if(APPLE)
   set(FFMPEG_EXTRA_FLAGS
     ${FFMPEG_EXTRA_FLAGS}
     --target-os=darwin
-    )
+    --x86asmexe=${LIBDIR}/nasm/bin/nasm
+  )
 endif()
 
 ExternalProject_Add(external_ffmpeg

build_files/build_environment/cmake/options.cmake

@@ -113,6 +113,10 @@ else()
       COMMAND xcode-select --print-path
       OUTPUT_VARIABLE XCODE_DEV_PATH OUTPUT_STRIP_TRAILING_WHITESPACE
     )
+    execute_process(
+      COMMAND xcodebuild -version -sdk macosx SDKVersion
+      OUTPUT_VARIABLE MACOSX_SDK_VERSION OUTPUT_STRIP_TRAILING_WHITESPACE)
+
     set(OSX_ARCHITECTURES x86_64)
     set(OSX_DEPLOYMENT_TARGET 10.11)
     set(OSX_SYSROOT ${XCODE_DEV_PATH}/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk)
@@ -155,6 +159,7 @@ else()
 
   set(CONFIGURE_ENV
     export MACOSX_DEPLOYMENT_TARGET=${OSX_DEPLOYMENT_TARGET} &&
+    export MACOSX_SDK_VERSION=${OSX_DEPLOYMENT_TARGET} &&
     export CFLAGS=${PLATFORM_CFLAGS} &&
     export CXXFLAGS=${PLATFORM_CXXFLAGS} &&
     export LDFLAGS=${PLATFORM_LDFLAGS}

build_files/build_environment/cmake/x264.cmake

@@ -21,12 +21,21 @@ if(WIN32)
 endif()
 
 
+if(APPLE)
+  set(X264_CONFIGURE_ENV
+    export AS=${LIBDIR}/nasm/bin/nasm
+  )
+else()
+  set(X264_CONFIGURE_ENV echo .)
+endif()
+
 ExternalProject_Add(external_x264
   URL ${X264_URI}
   DOWNLOAD_DIR ${DOWNLOAD_DIR}
   URL_HASH SHA256=${X264_HASH}
   PREFIX ${BUILD_DIR}/x264
-  CONFIGURE_COMMAND ${CONFIGURE_ENV} && cd ${BUILD_DIR}/x264/src/external_x264/ && ${CONFIGURE_COMMAND} --prefix=${LIBDIR}/x264
+  CONFIGURE_COMMAND ${CONFIGURE_ENV} && ${X264_CONFIGURE_ENV} && cd ${BUILD_DIR}/x264/src/external_x264/ &&
+    ${CONFIGURE_COMMAND} --prefix=${LIBDIR}/x264
     --enable-static
     --enable-pic
     --disable-lavf