是一种字符串处理的模式匹配方式, 作用是取CONFIG_CROSS_COMPILE 定义中有"" 括起来的数据值，如 CONFIG_CROSS_COMPILE="arm-none-linux-gnueabi-"则取出来的值即为arm-none-linux-gnueabi-，就是交叉编译器前缀。CONFIG_CROSS_COMPILE，通常由make menuconfig 配置时设定，保存如 arm 配置保存在arch/...
pkg-config does not by itself handle cross compilation situations. Since compiling for macOS x86_64 from ARM64 is very common, we need to handle this by configuring the right environment variables to make sure the build does not break by simply having pkg-config installed. This only applies ...