buildroot

strace: bump to version 4.21

Download site moved to strace.io. No upstream provided hashes.

Drop the musl specific autoconf seed values. These values are now
detected correctly.

Add --enable-mpers=check to fix configure on aarch64 that does not
support binaries for the compat personality.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>