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.

Jamfile

@@ -30,18 +30,27 @@ AddHaikuImagePackages [ FFilterByBuildFeatures
 		mesa mesa_devel mesa_swrast sed sharutils tar tiff wget which
 	}@
 ] ;
-# secondary architectures
-local architectureObject ;
-for architectureObject
-		in [ MultiArchSubDirSetup $(HAIKU_PACKAGING_ARCHS[2-]) ] {
-	on $(architectureObject) {
-		AddHaikuImagePackages [ FFilterByBuildFeatures
-			curl freetype icu libsolv zlib
+if $(HAIKU_PACKAGING_ARCHS[1]) != x86_gcc2 {
+	AddHaikuImagePackages [ FFilterByBuildFeatures gcc_syslibs ] ;
+}
 
-			regular_image @{
-				ffmpeg glu jpeg libpng mesa
-			}@
-		] ;
+if $(HAIKU_PACKAGING_ARCHS[2]) {
+	# secondary architectures
+	local architectureObject ;
+	for architectureObject
+			in [ MultiArchSubDirSetup $(HAIKU_PACKAGING_ARCHS[2-]) ] {
+		on $(architectureObject) {
+			AddHaikuImagePackages [ FFilterByBuildFeatures
+				curl freetype icu libsolv zlib
+
+				regular_image @{
+					ffmpeg glu jpeg libpng mesa
+				}@
+			] ;
+			if $(TARGET_PACKAGING_ARCH) != x86_gcc2 {
+				AddHaikuImagePackages [ FFilterByBuildFeatures gcc_syslibs ] ;
+			}
+		}
 	}
 }