init/gcov: allow CONFIG_CONSTRUCTORS on UML to fix module gcov

On ARCH=um, loading a module doesn't result in its constructors getting
called, which breaks module gcov since the debugfs files are never
registered.  On the other hand, in-kernel constructors have already been
called by the dynamic linker, so we can't call them again.

Get out of this conundrum by allowing CONFIG_CONSTRUCTORS to be
selected, but avoiding the in-kernel constructor calls.

Also remove the "if !UML" from GCOV selecting CONSTRUCTORS now, since we
really do want CONSTRUCTORS, just not kernel binary ones.

Link: https://lkml.kernel.org/r/20210120172041.c246a2cac2fb.I1358f584b76f1898373adfed77f4462c8705b736@changeid


Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Jessica Yu <jeyu@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>