build.sh: set ccache path based on ARCH

Author: frank-w

build.sh

@@ -102,6 +102,8 @@ if [[ ! $hostarch =~ aarch64|armv ]];then
 	fi
 
 	crosscompile=1
+	export CCACHE_DIR="$HOME/.cache/ccache/${ARCH}"
+	mkdir -p "${CCACHE_DIR}"
 fi;
 
 #if [[ "$builddir" != "" && ! "$1" =~ ^(updatesrc|uenv|defconfig|dts.?|[u]?mount)$ ]];