Adapt to ndk.hosts changes.

Test: ./build.py --toolchain aarch64-linux-android
Test: ./build.py --toolchain aarch64-linux-android --host windows
Test: ./build.py --toolchain aarch64-linux-android --host windows64
Bug: None
Exempt-From-Owner-Approval: trivial janitorial changes
Change-Id: I925c1f2ae303089fb2469ccfe3f09893548fce00
diff --git a/do_build.py b/do_build.py
index 908f7fd..b331437 100755
--- a/do_build.py
+++ b/do_build.py
@@ -21,8 +21,12 @@
 import site
 
 site.addsitedir(os.path.join(os.path.dirname(__file__), '../../ndk/build/lib'))
+site.addsitedir(os.path.join(os.path.dirname(__file__), '../../ndk'))
 
+# pylint: disable=import-error,wrong-import-position
 import build_support
+from ndk.hosts import Host
+# pylint: enable=import-error,wrong-import-position
 
 
 class ArgParser(build_support.ArgParser):
@@ -41,7 +45,7 @@
     if args.toolchain is not None:
         toolchains = [args.toolchain]
 
-    print('Building {} toolchains: {}'.format(args.host, ' '.join(toolchains)))
+    print(f'Building {args.host.value} toolchains: {" ".join(toolchains)}')
     for toolchain in toolchains:
         toolchain_name = '-'.join([toolchain, GCC_VERSION])
         sysroot_arg = '--sysroot={}'.format(
@@ -52,10 +56,10 @@
             sysroot_arg,
         ]
 
-        if args.host in ('windows', 'windows64'):
+        if args.host.is_windows:
             build_cmd.append('--mingw')
 
-        if args.host != 'windows':
+        if args.host != Host.Windows:
             build_cmd.append('--try-64')
 
         build_support.build(build_cmd, args)