Added '-Blinker' frontend driver option, allowing the linker search path

to be specified. This means swift can now cross-compile executables for
linux.

Author: springsup

include/swift/Option/Options.td

@@ -268,6 +268,10 @@ def use_ld : Joined<["-"], "use-ld=">,
   Flags<[DoesNotAffectIncrementalBuild]>,
   HelpText<"Specifies the linker to be used">;
 
+def ld_path : Separate<["-"], "Blinker">,
+  Flags<[FrontendOption, DoesNotAffectIncrementalBuild]>,
+  HelpText<"Specifies where to look for the linker">;
+
 def Xlinker : Separate<["-"], "Xlinker">,
   Flags<[DoesNotAffectIncrementalBuild]>,
   HelpText<"Specifies an option which should be passed to the linker">;

lib/Driver/ToolChains.cpp

@@ -1281,6 +1281,12 @@ toolchains::GenericUnix::constructInvocation(const LinkJobAction &job,
   if (!Linker.empty()) {
     Arguments.push_back(context.Args.MakeArgString("-fuse-ld=" + Linker));
   }
+  
+  // Add the linker search path
+  if (const Arg *A = context.Args.getLastArg(options::OPT_ld_path)) {
+    Arguments.push_back("-B");
+    Arguments.push_back(context.Args.MakeArgString(A->getValue()));
+  }
 
   std::string Target = getTargetForLinker();
   if (!Target.empty()) {