Don't duplicate flags when two version of 'darwin' or 'intel-linux'

are configured.

* tools/gcc.jam (init-link-flags): New parameter 'toolset'.
* tools/darwin.jam (init): Move flags inheriting out of here
* tools/intel-linux.jam (init): Likewise.


[SVN r25817]

tools/build

@@ -1 +1 @@
-Subproject commit b38c1978d303e2eb08ebceb257d8d75b141b1d4e
+Subproject commit 29985d877e13f88dfee40ce45fdfb983023f32a5