Forward -u to the linker on gnutools toolchains

Summary:
The BSDs and Darwin all forward the whole 'u' group, but gcc only
forwards -u so far as I can tell.  I only forward -u, since that's a
minimal change, and many people object to magically recognizing and
forwarding linker arguments.

Reviewers: chandlerc, joerg

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D4304

llvm-svn: 211756

clang/lib/Driver/Tools.cpp

@@ -7158,6 +7158,7 @@ void gnutools::Link::ConstructJob(Compilation &C, const JobAction &JA,
   }
 
   Args.AddAllArgs(CmdArgs, options::OPT_L);
+  Args.AddAllArgs(CmdArgs, options::OPT_u);
 
   const ToolChain::path_list Paths = ToolChain.getFilePaths();
 

clang/test/Driver/linux-ld.c

@@ -1119,3 +1119,9 @@
 // RUN:        --sysroot=%S/Inputs/basic_linux_tree 2>& 1 \
 // RUN:   | FileCheck --check-prefix=CHECK-PG %s
 // CHECK-PG: gcrt1.o
+
+// GCC forwards -u to the linker.
+// RUN: %clang -u asdf --target=x86_64-unknown-linux -### %s \
+// RUN:        --sysroot=%S/Inputs/basic_linux_tree 2>& 1 \
+// RUN:   | FileCheck --check-prefix=CHECK-u %s
+// CHECK-u: "-u" "asdf"