attestation: Add attestation.gyp to platform2.gyp

BUG=chromium:345099
TEST=See CL:188254

CQ-DEPEND=CL:191444, CL:188254

Change-Id: I56b637c83a3fa1dd237eb9aef4208d1992481415
Reviewed-on: https://chromium-review.googlesource.com/188252
Reviewed-by: Nam Nguyen <namnguyen@chromium.org>
Tested-by: Nam Nguyen <namnguyen@chromium.org>
Commit-Queue: Nam Nguyen <namnguyen@chromium.org>
diff --git a/platform.gyp b/platform.gyp
index a6522a1..93d5e27 100644
--- a/platform.gyp
+++ b/platform.gyp
@@ -56,6 +56,7 @@
             ['USE_tpm == 1', {
               'dependencies': [
                 '<(DEPTH)/chaps/chaps.gyp:*',
+                '<(DEPTH)/platform2/attestation/attestation.gyp:*',
               ],
             }],
             ['USE_vpn == 1', {