devel/root: Fix packaging of 6.34/02 on arm64

Packaging on arm64 is currently failing, because two header files are
missing, i.e. no longer included in the port.

> Building root-6.34.02

pkg-static: Unable to access file /wrkdirs/usr/ports/devel/root/work/stage/usr/local/etc/root/cling/lib/clang/18/include/arm_bf18.h:No such file or directory
pkg-static: Unable to access file /wrkdirs/usr/ports/devel/root/work/stage/usr/local/etc/root/cling/lib/clang/18/include/arm_fp18.h:No such file or directory

• Error code 1

See also: https://portsfallout.com/fallout?port=devel%2Froot%24&env=arm64
PR: 285048