Support Siso builds

This CL adds Siso build supports:
- Install Siso CIPD package.
- Generate //build/config/siso/.sisoenv file via DEPS hook.
- Generate `gn_logs.txt` GN logs.

Bug: 420355454
Change-Id: I6dd33ff12ba29167b00efbbe28712eec8527cc13
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/132390
Auto-Submit: Junji Watanabe <jwata@google.com>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>

.gitignore

diff --git a/.gitignore b/.gitignore
index 87a0a29..76b69be 100644
--- a/.gitignore
+++ b/.gitignore
@@ -35,6 +35,7 @@
 /third_party/rust
 /third_party/rust-toolchain
 /third_party/simdutf
+/third_party/siso
 /third_party/skia
 /third_party/test_fonts
 /third_party/zlib

BUILD.gn

diff --git a/BUILD.gn b/BUILD.gn
index 4edba9f..164be17 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -441,3 +441,17 @@
     deps += [ "//skia" ]
   }
 }
+
+# GN evaluates each .gn file once per toolchain, so restricting to default
+# toolchain will ensure write_file() is called only once.
+if (current_toolchain == default_toolchain) {
+  import("//build/gn_logs.gni")
+
+  # Write debug logs to gn_logs.txt.
+  _lines = [
+             "Generated during 'gn gen' by //BUILD.gn.",
+             "",
+           ] + build_gn_logs
+
+  write_file("$root_build_dir/gn_logs.txt", _lines)
+}

DEPS

diff --git a/DEPS b/DEPS
index b5977ab..a80f340 100644
--- a/DEPS
+++ b/DEPS
@@ -210,6 +210,10 @@
   # and whatever else without interference from each other.
   'simdutf_revision': '9d3e4d7c1afb30ed528443d73afab23f22443434',
   # Three lines of non-changing comments so that
+  # the commit queue can handle CLs rolling siso
+  # and whatever else without interference from each other.
+  'siso_version': 'git_revision:d9393c2115244b6e4a797189055e4a2b6769a64d',
+  # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling skia
   # and whatever else without interference from each other.
   'skia_revision': 'b82ac22e2deeae74c390cf735bc0d14d9658ada7',
@@ -538,6 +542,16 @@
     'condition': 'checkout_v8',
   },
 
+  'third_party/siso/cipd': {
+    'packages': [
+      {
+        'package': 'infra/build/siso/${{platform}}',
+        'version': Var('siso_version'),
+      }
+    ],
+    'dep_type': 'cipd',
+  },
+
   'third_party/skia': {
     'url': Var('skia_git') + '/skia.git@' + Var('skia_revision'),
     'condition': 'checkout_skia',
@@ -808,4 +822,14 @@
                '--quiet',
                ],
   },
+  # Configure Siso for developer builds.
+  {
+    'name': 'configure_siso',
+    'pattern': '.',
+    'action': ['python3',
+               'build/config/siso/configure_siso.py',
+               '--rbe_instance',
+               Var('rbe_instance'),
+               ],
+  },
 ]