`-C rpath` generates bad options for paths with commas

[jsgf]

-C rpath generates linker options of the form -Wl,-rpath,<path>. This fails if <path> contains commas, because -Wl, separates options on commas, so the linker ends up getting a bad path and spurious extra parameters.

The solution is to use -Xlinker which passes the next option through literally, so the full rpath can be specified with -Wl,-rpath -Xlinker <path,with,commas>. The -Xlinker form is fairly verbose, and only needed when there are commas.

(This comes up when building with Buck, because it generates paths of the form base/path/file.o#flavor1,flavor2 where "flavors" are things like "shared", "static", "pic", etc.)

[jsgf]

Fixed in 1.16