build: prepend ABI suffixes with a dash if package name ends with digit

build: prepend ABI suffixes with a dash if package name ends with digit

Ensure that ABI suffixes are separated with a dash from the package name if
the name happens to end with a digit. This implementation detail got lost
during the recent refactoring of the ABI_VERSION handling in buildroot.

Ref: https://github.com/openwrt/packages/pull/14237#issuecomment-860473585
Fixes: c921650382 ("build: drop ABI version from metadata")
Signed-off-by: Jo-Philipp Wich <jo@mein.io>
(cherry picked from commit f6a03bff5bccdbf9165087bccbb35095903d05c6)