tools: require coreutils to build elfutils
The version of the rmdir utility in macOS is POSIX-only
while elfutils uses the GNU extended options while building.
Tested-by: Georgi Valkov <[email protected]> # macOS
Signed-off-by: Michael Pratt <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/16522
Signed-off-by: Robert Marko <[email protected]>