hadrian: Fix mention of non-existent removeFiles function
Previously Hadrian's bindist Makefile referred to a removeFiles
function that was previously defined by the make
build system. Since
the make
build system is no longer around, this function is now
undefined. Naturally, make being make, this appears to be silently
ignored instead of producing an error.
Fix this by rewriting it to rm -f
.
Closes #23373 (closed).