Build failed on macos

[star-hengxing]

  Target "dispatch" links to:

    BlocksRuntime::BlocksRuntime

  but the target was not found.  Possible reasons include:

    * There is a typo in the target name.
    * A find_package call is missing for an IMPORTED target.
    * An ALIAS target is missing.

Why?

swift-corelibs-libdispatch/src/CMakeLists.txt

Lines 153 to 154 in 0bb6c10

	target_link_libraries(dispatch PUBLIC
	BlocksRuntime::BlocksRuntime)

[zhuzhidong]

macOS 系统本身已经内置 Blocks 运行时，无需单独安装 libBlocksRuntime，此时显示链接外部 BlockRuntime 库，会导致找不到目标。
直接删除就可以了，或者可以通过条件编译来区分。

if(APPLE)
    xxxx
else()
    xxxx
endif()