Check in the libxslt roll script.

third_party/libxslt/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 config("libxslt_config") {
   defines = [ "LIBXSLT_STATIC" ]
-  include_dirs = [ "." ]
+  include_dirs = [ "src" ]
 }
 
 config("libxslt_warnings") {
   if (is_clang) {
     cflags = [
       # libxslt stores a char[3] in a `const unsigned char*`.
       "-Wno-pointer-sign",
 
       # xsltDefaultRegion and xsltCalibrateTimestamps are only
       # used with certain preprocessor defines set.
       "-Wno-unused-function",
     ]
   }
 }
 
 static_library("libxslt") {
   sources = [
-    "libxslt/attributes.c",
-    "libxslt/attributes.h",
-    "libxslt/attrvt.c",
-    "libxslt/documents.c",
-    "libxslt/documents.h",
-    "libxslt/extensions.c",
-    "libxslt/extensions.h",
-    "libxslt/extra.c",
-    "libxslt/extra.h",
-    "libxslt/functions.c",
-    "libxslt/functions.h",
-    "libxslt/imports.c",
-    "libxslt/imports.h",
-    "libxslt/keys.c",
-    "libxslt/keys.h",
-    "libxslt/libxslt.h",
-    "libxslt/namespaces.c",
-    "libxslt/namespaces.h",
-    "libxslt/numbers.c",
-    "libxslt/numbersInternals.h",
-    "libxslt/pattern.c",
-    "libxslt/pattern.h",
-    "libxslt/preproc.c",
-    "libxslt/preproc.h",
-    "libxslt/security.c",
-    "libxslt/security.h",
-    "libxslt/templates.c",
-    "libxslt/templates.h",
-    "libxslt/transform.c",
-    "libxslt/transform.h",
-    "libxslt/trio.h",
-    "libxslt/triodef.h",
-    "libxslt/variables.c",
-    "libxslt/variables.h",
-    "libxslt/win32config.h",
-    "libxslt/xslt.c",
-    "libxslt/xslt.h",
-    "libxslt/xsltInternals.h",
-    "libxslt/xsltconfig.h",
-    "libxslt/xsltexports.h",
-    "libxslt/xsltlocale.c",
-    "libxslt/xsltlocale.h",
-    "libxslt/xsltutils.c",
-    "libxslt/xsltutils.h",
-    "libxslt/xsltwin32config.h",
+    "src/libxslt/attributes.c",
+    "src/libxslt/attributes.h",
+    "src/libxslt/attrvt.c",
+    "src/libxslt/documents.c",
+    "src/libxslt/documents.h",
+    "src/libxslt/extensions.c",
+    "src/libxslt/extensions.h",
+    "src/libxslt/extra.c",
+    "src/libxslt/extra.h",
+    "src/libxslt/functions.c",
+    "src/libxslt/functions.h",
+    "src/libxslt/imports.c",
+    "src/libxslt/imports.h",
+    "src/libxslt/keys.c",
+    "src/libxslt/keys.h",
+    "src/libxslt/libxslt.h",
+    "src/libxslt/namespaces.c",
+    "src/libxslt/namespaces.h",
+    "src/libxslt/numbers.c",
+    "src/libxslt/numbersInternals.h",
+    "src/libxslt/pattern.c",
+    "src/libxslt/pattern.h",
+    "src/libxslt/preproc.c",
+    "src/libxslt/preproc.h",
+    "src/libxslt/security.c",
+    "src/libxslt/security.h",
+    "src/libxslt/templates.c",
+    "src/libxslt/templates.h",
+    "src/libxslt/transform.c",
+    "src/libxslt/transform.h",
+    "src/libxslt/trio.h",
+    "src/libxslt/triodef.h",
+    "src/libxslt/variables.c",
+    "src/libxslt/variables.h",
+    "src/libxslt/win32config.h",
+    "src/libxslt/xslt.c",
+    "src/libxslt/xslt.h",
+    "src/libxslt/xsltInternals.h",
+    "src/libxslt/xsltconfig.h",
+    "src/libxslt/xsltexports.h",
+    "src/libxslt/xsltlocale.c",
+    "src/libxslt/xsltlocale.h",
+    "src/libxslt/xsltutils.c",
+    "src/libxslt/xsltutils.h",
+    "src/libxslt/xsltwin32config.h",
     "linux/config.h",
     "mac/config.h",
     "win32/config.h",
   ]
 
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [
     "//build/config/compiler:no_chromium_code",
 
     # Must be after no_chromium_code for warning flags to be ordered correctly.
@@ skipping 14 matching lines @@
       "/wd4311",
     ]
   } else if (is_mac) {
     include_dirs = [ "mac" ]
   }
 
   deps = [
     "//third_party/libxml",
   ]
 }