Disable default debugging dumps for libomptarget and plugins and move dumps
under control of environment variable LIBOMPTARGET_DEBUG=<integer>. Dumps
are enabled when LIBOMPTARGET_DEBUG is set to a positive integer value.
Debugging dumps are available only in debug build; release build does not
support it.
Differential Revision: https://reviews.llvm.org/D33227
llvm-svn: 310841
Sergey Dmitriev