Use libstdc++, libsupc++ and libgcc from gcc_syslibs.

* Instead of faking libstdc++.so from libstdc++.a, use libstdc++.so
  from the gcc_syslibs build feature for everything except x86_gcc2.
* Use libgcc_s.so from the gcc_syslibs build feature for everything but
  x86_gcc2 (which still carries libgcc as part of libroot.so).
* Drop filtering of libgcc objects for libroot, as that is no longer
  necessary since we're only using libgcc-as-single-object for libroot
  with x86_gcc2, where the filtered object file doesn't exist. Should
  the objects that used to be filtered cause any problems as part of
  libgcc_s.so, we can always filter them as part of the gcc build.
* Use libsupc++.so from the gcc_syslibs build feature for everything but
  x86_gcc2.
* Adjust all Jamfiles accordingly.
* Deactivate building of faked libstdc++.so for non-x86-gcc2. For
  x86_gcc2, we still build libstdc++.so from the sources in the Haiku
  source tree as part of the Haiku build .
* Put gcc_syslibs package onto the image, when needed.

build/jam/MainBuildRules

@@ -8,7 +8,8 @@ rule AddSharedObjectGlueCode
 	on $(1) {
 		platform = $(PLATFORM) ;
 		if $(platform) = haiku {
-			local stdLibs = [ MultiArchDefaultGristFiles libroot.so ] ;
+			local stdLibs = [ MultiArchDefaultGristFiles libroot.so ]
+				[ TargetLibgcc ] ;
 			local type = EXECUTABLE ;
 			if $(2) != true {
 				type = LIBRARY ;