Windows: Ignore INCLUDE/LIB env if vcvarsall.bat is available (see issue #2773)

Windows ARM64 cross-compile requires building Clang x64 binaries. Building both
arm64 and x64 binaries in the same build is not possible when using INCLUDE/LIB
values set via the environment. Instead, allow Chromium to extract the correct
configuration from vcvarsall.bat for populating the environment.[arch] files.

tools/gclient_hook.py

@@ -56,10 +56,10 @@ if platform == 'windows':
   if not 'DEPOT_TOOLS_WIN_TOOLCHAIN' in os.environ:
     os.environ['DEPOT_TOOLS_WIN_TOOLCHAIN'] = '0'
 
-  # By default GN+Ninja on Windows expects Visual Studio to be installed on
-  # the local machine. To build when Visual Studio is extracted to a directory
-  # but not installed (e.g. via a custom toolchain) set the following
-  # environment variables:
+  # By default GN+Ninja on Windows expects Visual Studio and Windows SDK to be
+  # installed on the local machine. To build when Visual Studio and/or SDK is
+  # extracted to a directory but not installed (e.g. via a custom toolchain) set
+  # the following environment variables:
   #
   # o Enable use of a custom toolchain on Windows.
   #
@@ -78,10 +78,11 @@ if platform == 'windows':
   #   should instead be discoverable via the PATH env variable.
   #   (b) build/toolchain/win/setup_toolchain.py _LoadToolchainEnv when
   #   writing environment.* files that specify INCLUDE/LIB/PATH values. If
-  #   "%GYP_MSVS_OVERRIDE_PATH%\VC\vcvarsall.bat" exists then environment
-  #   variables will be derived from there and the specified INCLUDE/LIB/PATH
-  #   values will be ignored by Chromium. If this file does not exist then the
-  #   INCLUDE/LIB/PATH values are also required by Chromium.
+  #   vcvarsall.bat [1] exists then environment variables will be derived from
+  #   there and the specified INCLUDE/LIB values will be ignored by Chromium
+  #   (PATH is retained because it might contain required VS runtime libraries).
+  #   If this file does not exist then the INCLUDE/LIB/PATH values are also
+  #   required by Chromium.
   #   TODO(cef): Rename to VS_ROOT and VS_VERSION after Chromium cleans up GYP
   #   dependencies.
   #
@@ -93,10 +94,8 @@ if platform == 'windows':
   #   set VS_CRT_ROOT=<VS CRT root directory>
   #   set SDK_ROOT=<Platform SDK root directory>
   #
-  # o Used by various scripts as described above.
-  #   TODO(cef): Make these values optional when
-  #   "%GYP_MSVS_OVERRIDE_PATH%\VC\vcvarsall.bat" exists (use values from that
-  #   script instead).
+  # o Used by various scripts as described above. These values are optional when
+  #   vcvarsall.bat [1] exists.
   #
   #   set INCLUDE=<VS include paths>
   #   set LIB=<VS library paths>
@@ -106,6 +105,13 @@ if platform == 'windows':
   # packaging script along with required directory contents and INCLUDE/LIB/PATH
   # values.
   #
+  # [1] The vcvarsall.bat script must exist in "%GYP_MSVS_OVERRIDE_PATH%\VC\" or
+  #     "%GYP_MSVS_OVERRIDE_PATH%\VC\Auxiliary\Build\". If the Windows SDK is not
+  #     installed (e.g. not discoverable via the Windows registry) then
+  #     "%GYP_MSVS_OVERRIDE_PATH%\Common7\Tools\vsdevcmd\core\winsdk.bat" must be
+  #     patched to support discovery via SDK_ROOT as described in
+  #     https://bitbucket.org/chromiumembedded/cef/issues/2773#comment-59687474.
+  #
   if bool(int(os.environ.get('WIN_CUSTOM_TOOLCHAIN', '0'))):
     required_vars = [
         'CEF_VCVARS',
@@ -113,9 +119,6 @@ if platform == 'windows':
         'GYP_MSVS_VERSION',
         'VS_CRT_ROOT',
         'SDK_ROOT',
-        'INCLUDE',
-        'LIB',
-        'PATH',
     ]
     for var in required_vars:
       if not var in os.environ.keys():

tools/gn_args.py

@@ -384,6 +384,8 @@ def ValidateArgs(args):
     #   GYP_MSVS_OVERRIDE_PATH=<path to VS root, must match visual_studio_path>
     #   GYP_MSVS_VERSION=<VS version, must match visual_studio_version>
     #   CEF_VCVARS=none
+    #
+    # Optional environment variables (required if vcvarsall.bat does not exist):
     #   INCLUDE=<VS include paths>
     #   LIB=<VS library paths>
     #   PATH=<VS executable paths>
@@ -409,18 +411,27 @@ def ValidateArgs(args):
       assert os.environ.get('CEF_VCVARS', '') == 'none', \
         "visual_studio_path requires CEF_VCVARS=none env variable"
 
-      assert 'INCLUDE' in os.environ \
-        and 'LIB' in os.environ \
-        and 'PATH' in os.environ, \
-        "visual_studio_path requires INCLUDE, LIB and PATH env variables"
-
-      # If "%GYP_MSVS_OVERRIDE_PATH%\VC\vcvarsall.bat" exists then environment
-      # variables will be derived from there and the specified INCLUDE/LIB/PATH
-      # values will be ignored by Chromium. If this file does not exist then the
-      # INCLUDE/LIB/PATH values are also required by Chromium.
+      # If vcvarsall.bat exists then environment variables will be derived from
+      # there and any specified INCLUDE/LIB values will be ignored by Chromium
+      # (PATH is retained because it might contain required VS runtime
+      # libraries). If this file does not exist then the INCLUDE/LIB/PATH values
+      # are also required by Chromium.
       vcvars_path = os.path.join(msvs_path, 'VC', 'vcvarsall.bat')
-      if (os.path.exists(vcvars_path)):
-        msg('INCLUDE/LIB/PATH values will be derived from %s' % vcvars_path)
+      if not os.path.exists(vcvars_path):
+        vcvars_path = os.path.join(msvs_path, 'VC', 'Auxiliary', 'Build',
+                                   'vcvarsall.bat')
+      if os.path.exists(vcvars_path):
+        if 'INCLUDE' in os.environ:
+          del os.environ['INCLUDE']
+        if 'LIB' in os.environ:
+          del os.environ['LIB']
+        if 'LIBPATH' in os.environ:
+          del os.environ['LIBPATH']
+      else:
+        assert 'INCLUDE' in os.environ \
+          and 'LIB' in os.environ \
+          and 'PATH' in os.environ, \
+          "visual_studio_path requires INCLUDE, LIB and PATH env variables"
 
 
 def GetConfigArgs(args, is_debug, cpu):