Set BUILD_DIR=out in xcodebuild invocation for Mac and remove conditional LIBUV_BUILD variable, so both platforms consistently use build/libuv/out/Release/libuv.a instead of Mac using build/libuv/build/Release/libuv.a.
Set BUILD_DIR=out in xcodebuild invocation for Mac and remove conditional LIBUV_BUILD variable, so both platforms consistently use build/libuv/out/Release/libuv.a instead of Mac using build/libuv/build/Release/libuv.a.