Pull Linux host tools from cipd

Bug: 118
Change-Id: Ic2d25419c7addd64b87641f2d7254109d059f7af
diff --git a/pw_env_setup/py/pw_env_setup/cipd_setup/pigweed.json b/pw_env_setup/py/pw_env_setup/cipd_setup/pigweed.json
index 4c74874..dbc12b2 100644
--- a/pw_env_setup/py/pw_env_setup/cipd_setup/pigweed.json
+++ b/pw_env_setup/py/pw_env_setup/cipd_setup/pigweed.json
@@ -87,5 +87,12 @@
         "tags": [
             "version:8.1.0"
         ]
+    },
+    {
+        "path": "pigweed/host_tools/${os=linux}-${arch=amd64}",
+        "tags": [
+            "git_revision:25527c09720fcc8920f21ee5c93f71ee636ea96a"
+        ],
+        "_comment": "TODO(pwbug/118) Put Windows and Mac host tools in CIPD."
     }
 ]
diff --git a/pw_env_setup/py/pw_env_setup/host_build_setup.py b/pw_env_setup/py/pw_env_setup/host_build_setup.py
index 30f2e38..11c7a0f 100644
--- a/pw_env_setup/py/pw_env_setup/host_build_setup.py
+++ b/pw_env_setup/py/pw_env_setup/host_build_setup.py
@@ -14,11 +14,20 @@
 """Builds and sets up environment to use host build."""
 
 import os
+import platform
 import subprocess
 
 
 def install(pw_root, env):
     host_dir = os.path.join(pw_root, 'out', 'host')
+    env.prepend('PATH', os.path.join(host_dir, 'host_tools'))
+
+    if platform.system() == 'Linux':
+        msg = 'skipping host tools setup--got from CIPD'
+        print(msg)
+        env.echo(msg)
+        return
+
     with env():
         try:
             gn_gen = [
@@ -33,5 +42,3 @@
 
         except subprocess.CalledProcessError:
             env.echo('warning: host tools failed to build')
-
-    env.prepend('PATH', os.path.join(host_dir, 'host_tools'))