Auto merge of #20543 - kwonoj:chore-bulid-win32, r=jdm

build(mach): locate vs via vswhere on win32

<!-- Please describe your changes on the following line: -->
This PR tries to improve Visual Studio installation lookup in mach.

It includes changes
- lookup VS2017 installation via `vswhere` (https://github.com/Microsoft/vswhere) allows non-default location installation eventually.
: currently PR does uses vswhere binary from VS installation itself, but vswhere binary can be placed separately without VS (github repo publishes binary releases also) - allows VS lookup without any dependency to binary / path / or env variables. For VS15, it falls back to same logic based on file path as vswhere supports from VS17 and above.

- assign environment variable in python process
: This is mostly for some non-default win32 environment who doesn't uses cmd.exe as default shell (myself). For example, if default shell is zsh, running vcvarsall.bat doesn't inherit env variable into current shell. Instead, this PR borrows implementation of Electron (https://github.com/electron/electron/blob/master/script/lib/env_util.py) which established inheriting env variable into python process itself, doesn't care about primary shell invoked scripts.

Still `mach.bat` remains for compatibility purpose, but `mach` take cares of all of jobs.

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [x] `./mach build -d` does not report any errors
- [ ] `./mach build-geckolib` does not report any errors
- [ ] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

<!-- Either: -->
- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because _____
- Locally built & run on windows machine
<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

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mach

@@ -11,8 +11,9 @@
 
 from __future__ import print_function, unicode_literals
 
-
+import itertools
 import os
+import subprocess
 import sys
 
 
@@ -23,9 +24,104 @@ def main(args):
     mach = mach_bootstrap.bootstrap(topdir)
     sys.exit(mach.run(sys.argv[1:]))
 
+def validate_pair(ob):
+  if not (len(ob) == 2):
+    print("Unexpected result:", ob, file=sys.stderr)
+    return False
+  else:
+    return True
+
+def consume(iter):
+  try:
+    while True: next(iter)
+  except StopIteration:
+    pass
+
+def get_environment_from_batch_command(env_cmd, initial=None):
+  """
+  Take a command (either a single command or list of arguments)
+  and return the environment created after running that command.
+  Note that if the command must be a batch file or .cmd file, or the
+  changes to the environment will not be captured.
+  If initial is supplied, it is used as the initial environment passed
+  to the child process.
+  """
+  if not isinstance(env_cmd, (list, tuple)):
+    env_cmd = [env_cmd]
+  # Construct the command that will alter the environment.
+  env_cmd = subprocess.list2cmdline(env_cmd)
+  # Create a tag so we can tell in the output when the proc is done.
+  tag = 'END OF BATCH COMMAND'
+  # Construct a cmd.exe command to do accomplish this.
+  cmd = 'cmd.exe /s /c "{env_cmd} && echo "{tag}" && set"'.format(**vars())
+  # Launch the process.
+  proc = subprocess.Popen(cmd, stdout=subprocess.PIPE, env=initial)
+  # Parse the output sent to stdout.
+  lines = proc.stdout
+  # Consume whatever output occurs until the tag is reached.
+  consume(itertools.takewhile(lambda l: tag not in l, lines))
+  # Define a way to handle each KEY=VALUE line.
+  handle_line = lambda l: l.rstrip().split('=',1)
+  # Parse key/values into pairs.
+  pairs = map(handle_line, lines)
+  # Make sure the pairs are valid.
+  valid_pairs = filter(validate_pair, pairs)
+  # Construct a dictionary of the pairs.
+  result = dict(valid_pairs)
+  # Let the process finish.
+  proc.communicate()
+  return result
+
+def get_vs_env(vs_version, arch):
+  """
+  Returns the env object for VS building environment.
+  The vs_version can be strings like "[15.0,16.0)", meaning 2017, but not the next version.
+  The arch has to be one of "x86", "amd64", "arm", "x86_amd64", "x86_arm", "amd64_x86",
+  "amd64_arm", e.g. the args passed to vcvarsall.bat.
+  """
+
+  # vswhere can't handle spaces, like "[15.0, 16.0)" should become "[15.0,16.0)"
+  vs_version = vs_version.replace(" ", "")
+
+  # Find visual studio
+  proc = subprocess.Popen(
+    "C:\\Program Files (x86)\\Microsoft Visual Studio\\Installer\\vswhere.exe "
+    "-property installationPath "
+    "-requires Microsoft.VisualStudio.Component.VC.CoreIde "
+    "-format value "
+    "-version {0}".format(vs_version),
+    stdout=subprocess.PIPE)
+
+  location = proc.stdout.readline().rstrip()
+  # Launch the process.
+  vsvarsall = "{0}\\VC\\Auxiliary\\Build\\vcvarsall.bat".format(location)
+
+  return get_environment_from_batch_command([vsvarsall, arch])
+
+def import_vs_env():
+    if sys.platform != 'win32':
+        return
+
+    if ('PROGRAMFILES(X86)' in os.environ) == False:
+        print('32-bit Windows is currently unsupported.')
+        sys.exit(-1)
+
+    arch = 'x64'
+    if os.path.isfile("C:\\Program Files (x86)\\Microsoft Visual Studio\\Installer\\vswhere.exe"):
+        env = get_vs_env('[15.0,16.0)', arch)
+        os.environ.update(env)
+    elif 'VS140COMNTOOLS' in os.environ:
+        vs14vsvarsall = os.path.abspath(os.path.join(os.environ['VS140COMNTOOLS'], '..\\..\\VC\\vcvarsall.bat'))
+        env = get_environment_from_batch_command([vs14vsvarsall, arch])
+        os.environ.update(env)
+    else:
+        print("Visual Studio 2017 is not installed.\nDownload and install Visual Studio 2017 from https://www.visualstudio.com/")
+        sys.exit(-1)
 
 if __name__ == '__main__':
     sys.dont_write_bytecode = True
+    import_vs_env()
+
     if sys.platform == 'win32':
         # This is a complete hack to work around the fact that Windows
         # multiprocessing needs to import the original module (ie: this

mach.bat

@@ -1,39 +1,2 @@
 @echo off
-
-pushd .
-
-IF EXIST "%ProgramFiles(x86)%" (
-  set "ProgramFiles32=%ProgramFiles(x86)%"
-) ELSE (
-  set "ProgramFiles32=%ProgramFiles%"
-)
-
-set VC14VARS=%VS140COMNTOOLS%..\..\VC\vcvarsall.bat
-IF EXIST "%VC14VARS%" (
-  set "VS_VCVARS=%VC14VARS%"
-) ELSE (
-  for %%e in (Enterprise Professional Community BuildTools) do (
-    IF EXIST "%ProgramFiles32%\Microsoft Visual Studio\2017\%%e\VC\Auxiliary\Build\vcvarsall.bat" (
-      set "VS_VCVARS=%ProgramFiles32%\Microsoft Visual Studio\2017\%%e\VC\Auxiliary\Build\vcvarsall.bat"
-    )
-  )
-)
-
-IF EXIST "%VS_VCVARS%" (
-  IF NOT DEFINED Platform (
-    IF EXIST "%ProgramFiles(x86)%" (
-      call "%VS_VCVARS%" x64
-    ) ELSE (
-      ECHO 32-bit Windows is currently unsupported.
-      EXIT /B
-    )
-  )
-) ELSE (
-  ECHO Visual Studio 2015 or 2017 is not installed.
-  ECHO Download and install Visual Studio 2015 or 2017 from https://www.visualstudio.com/
-  EXIT /B
-)
-
-popd
-
 python mach %*