Update to use x64 instead of x86-64

Change-Id: I433a0f816dbf7f2f2250a809ee7259956b176b15
diff --git a/README.md b/README.md
index 40ec4e2..a68185f 100644
--- a/README.md
+++ b/README.md
@@ -55,7 +55,7 @@
 
     ./scripts/fx set-layer garnet
     .jiri_root/bin/jiri update
-    ./scripts/fx set x86 --release
+    ./scripts/fx set x64 --release
     ./scripts/fx build-zircon
     ./scripts/fx build
 
diff --git a/src/sdk.rs b/src/sdk.rs
index 13e946d..c6fe7b5 100644
--- a/src/sdk.rs
+++ b/src/sdk.rs
@@ -35,8 +35,8 @@
     pub fn new(release_os: bool, device_name: Option<&'a str>) -> TargetOptions {
         TargetOptions {
             release_os: release_os,
-            target_cpu: "x86-64",
-            target_cpu_linker: "x86_64",
+            target_cpu: "x64",
+            target_cpu_linker: "x64",
             device_name: device_name,
         }
     }
@@ -63,8 +63,8 @@
             } else {
                 bail!(
                     "FUCHSIA_ROOT not set and current directory is not in a Fuchsia tree with a \
-                    release-x86-64 build. You must set the environmental variable FUCHSIA_ROOT to \
-                    point to a Fuchsia tree with a release-x86-64 build."
+                    release-x64 build. You must set the environmental variable FUCHSIA_ROOT to \
+                    point to a Fuchsia tree with a release-x64 build."
                 )
             }
         }
@@ -108,7 +108,7 @@
 
 pub fn sysroot_path(options: &TargetOptions) -> Result<PathBuf, Error> {
     let zircon_name =
-        if options.target_cpu == "x86-64" { "build-user-x86-64" } else { "build-user-arm64" };
+        if options.target_cpu == "x64" { "build-x64" } else { "build-arm64" };
     Ok(fuchsia_root(&options)?.join("out").join("build-zircon").join(zircon_name).join("sysroot"))
 }