libstdc++: Fix error shown during Solaris build

libstdc++: Fix error shown during Solaris build

Currently this is shown when building libstdc++ on Solaris:

-lrt: open: No such file or directory

The error comes from the make_sunver.pl script which tries to open each
of its arguments. The arguments are passed by this make rule:

	perl ${glibcxx_srcdir}/scripts/make_exports.pl \
	  libstdc++-symbols.ver \
	  $(libstdc___la_OBJECTS:%.lo=.libs/%.o) \
	 `echo $(libstdc___la_LIBADD) | \
	    sed 's,/\([^/.]*\)\.la,/.libs/\1.a,g'` \
	 > $@ || (rm -f $@ ; exit 1)

The $(libstdc___la_LIBADD) variable includes $(GLIBCXX_LIBS) which
contains -lrt on Solaris.

This patch adds another sed script to filter -l arguments from the echo
command. In order to reliably match ' -l[^ ]* ' the echo arguments are
quoted and a space added before and after them. This might be overkill
just to remove -lrt from the start of the string, but should be robust
in case other -l arguments are added to $(GLIBCXX_LIBS), or in case the
$(libstdc___la_LIBADD) libraries are reordered.

libstdc++-v3/ChangeLog:

	* src/Makefile.am (libstdc++-symbols.ver-sun): Remove -lrt from
	arguments passed to make_sunver.pl script.
	* src/Makefile.in: Regenerate.