PPC/s390: [sysroot installer] Disable for host arch PPC/s390

Since PPC/s390 doesn't have the sysroot files available
on google storage, disabling it so that the script doesn't
cause gclient sync to fail when run on PPC/s390.

[email protected]

BUG=
LOG=N

Review-Url: https://codereview.chromium.org/2382883003
Cr-Commit-Position: refs/heads/master@{#422014}
diff --git a/AUTHORS b/AUTHORS
index b8dee18..e448c92 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -279,6 +279,7 @@
 Jaekyeom Kim <[email protected]>
 Jaemin Seo <[email protected]>
 Jaeseok Yoon <[email protected]>
+Jaideep Bajwa <[email protected]>
 Jaime Soriano Pastor <[email protected]>
 Jake Helfert <[email protected]>
 Jakob Weigert <[email protected]>
@@ -776,3 +777,4 @@
 Yandex LLC <*@yandex-team.ru>
 ARM Holdings <*@arm.com>
 Macadamian <*@macadamian.com>
+IBM Inc. <*@*.ibm.com>