Support for RUNTESTFLAGS in DejaGnu test harness for libstdc++-v3?

[Loren James Rittle <rittle at latour dot rsch dot comm dot mot dot com>]

The new DejaGnu test harness for libstc++-v3 doesn't honor the
``schedule of variations'' as other parts of gcc does.

For example (your shell syntax will vary slightly):

  ; gmake -C gcc RUNTESTFLAGS\='--target_board ''unix{-pthreads}''' check-g++

will run the g++ test suite but add -pthreads to all compilation command lines.

However, this command line:

  ; gmake -C i386-unknown-freebsd4.2/libstdc++-v3 \
	RUNTESTFLAGS\='--target_board ''unix{-pthreads}''' check

doesn't pass RUNTESTFLAGS to the Makefile in libstdc++-v3/testsuite
(this is important since the top-level Makefile allows one to put
RUNTESTFLAGS in their environment and it propagates it down to other,
recursively-called Makefiles).

And, this command line:

  ; gmake -C i386-unknown-freebsd4.2/libstdc++-v3/testsuite \
	RUNTESTFLAGS\='--target_board ''unix{-pthreads}''' check

reports the schedule of variations as ``unix/-pthreads'' once the
libstdc++ tests begins but the scheduled options are dropped
(i.e. checking the log reveals that -pthread was added to none of
compilation command lines).

This is not an obvious regression from before the conversion to
dejagnu (one had to hand-edit a file), but it is a remaining
difference from how the rest of the tree works.  At some point, this
will annoy me enough to fix but in case it is obvious to our fearless
dejagnu test harness writer, I post this now... ;-)

Regards,
Loren