gn build: Stop passing -o to ar.

The -o flag means something different to ar than what appears to be
intended here. Also, llvm-ar doesn't accept the flag in this position.

Differential Revision: https://reviews.llvm.org/D56426

llvm-svn: 350604

utils/gn/build/toolchain/BUILD.gn

@@ -51,7 +51,7 @@ toolchain("unix") {
       # Remove the output file first so that ar doesn't try to modify the
       # existing file.
       command =
-          "rm -f {{output}} && ar rcsDT {{arflags}} -o {{output}} {{inputs}}"
+          "rm -f {{output}} && ar rcsDT {{arflags}} {{output}} {{inputs}}"
     }
     description = "AR {{output}}"
     outputs = [