Add 'ThinLTO Linux ToT' buildbot (src part).

tools/mb/mb_config.pyl

Index: tools/mb/mb_config.pyl
diff --git a/tools/mb/mb_config.pyl b/tools/mb/mb_config.pyl
index e0587d3f1912126139d2a4f46139cfca706622da..d42e836ae3cc2cfa1d584abe44eadfe64b4a8cc9 100644
--- a/tools/mb/mb_config.pyl
+++ b/tools/mb/mb_config.pyl
@@ -257,6 +257,7 @@
       'Mojo Windows': 'gn_release_bot_minimal_symbols_x86',
       'Site Isolation Linux': 'gn_release_trybot',
       'Site Isolation Win': 'gn_release_trybot_x86',
+      'ThinLTO Linux ToT': 'gn_thin_lto_clang_tot_release_bot',
       'UBSanVptr Linux': 'gn_ubsan_vptr_release_bot',
       'WebKit Linux - TraceWrappables': 'swarming_gn_release_bot_x64',
       'WebKit Linux - WPTServe': 'swarming_gn_release_bot',
@@ -1540,6 +1541,10 @@
       'gn', 'syzyasan', 'no_pch', 'release', 'x86',
     ],
 
+    'gn_thin_lto_clang_tot_release_bot': [
+      'gn', 'thin_lto', 'clang_tot', 'release_bot',
+    ],
+
     'gn_tsan_disable_nacl_line_tables_debug_bot': [
       'gn', 'tsan', 'disable_nacl', 'line_tables', 'debug_bot',
     ],
@@ -2445,6 +2450,11 @@
       'gyp_defines': 'syzyasan=1'
     },
 
+    'thin_lto': {
+      'gn_args': 'use_thin_lto=true',
+      'mixins': ['cfi'],
+    },
+
     'tsan': {
       'gn_args': 'is_tsan=true',
       'gyp_defines': 'tsan=1',