Fix some faults in util/mk1mf.pl

When building on Unix, there are times when the 'EX_LIB' MINFO variable
contains valuable information.  Make sure to take care of it.

fixrules in util/pl/unix.pl was previously changed with a simpler fix of
rules, with a comment claiming that's compatible with -j.  Unfortunately,
this breaks multiline rules and doesn't change anything for single line
rules.  While at it, do not prefix pure echo lines with a 'cd $(TEST_D) &&',
as that's rather silly.

Reviewed-by: Andy Polyakov <appro@openssl.org>