Fix parsing of rpaths which include spaces in runInjectRPaths (8.10)

The logic didn't account for the fact that the paths could contain spaces before which led to errors such as the following from install_name_tool.

Stderr ( T14304 ):
Warning: -rtsopts and -with-rtsopts have no effect with -shared.
    Call hs_init_ghc() from your main() function to set these options.
error: /nix/store/a6j5761iy238pbckxq2xrhqr2d5kra4m-cctools-binutils-darwin-949.0.1/bin/install_name_tool: for: dist/build/libHSp-0.1-ghc8.10.6.dylib (for architecture arm64) option "-add_rpath /Users/matt/ghc/bindisttest/install   dir/lib/ghc-8.10.6/ghc-prim-0.6.1" would duplicate path, file already has LC_RPATH for: /Users/matt/ghc/bindisttest/install   dir/lib/ghc-8.10.6/ghc-prim-0.6.1
`install_name_tool' failed in phase `Install Name Tool'. (Exit code: 1)

Fixes #20212 (closed)