Solve some PATH issues on Windows

bootstrap.js

@@ -28,10 +28,12 @@ if (!fs.existsSync(path.join('vendor', 'depot_tools')))
 
 // Getting the code.
 if (!skipGclient) {
-  let args = ''
+  let args = '--with_branch_heads --with_tags'
   if (force)
     args += ' --force'
-  execSync(`gclient sync --with_branch_heads --with_tags ${args}`)
+  // Calling gclient directly would invoke gclient.bat on Windows, which does
+  // not work prefectly under some shells.
+  execSync(`python vendor/depot_tools/gclient.py sync ${args}`)
 }
 
 // Switch to src dir.
@@ -47,5 +49,5 @@ const sccachePath = path.resolve('electron', 'external_binaries', 'sccache')
 for (const name in configs) {
   const config = targetCpu === 'x64' ? name : `${name}_${targetCpu}`
   const gnArgs = `import("//electron/build/args/${configs[name]}.gn") ${extraArgs} target_cpu="${targetCpu}" cc_wrapper="${sccachePath}"`
-  spawnSync('gn', ['gen', `out/${config}`, `--args=${gnArgs}`])
+  spawnSync('python', ['third_party/depot_tools/gn.py', 'gen', `out/${config}`, `--args=${gnArgs}`])
 }

lib/common.js

@@ -23,8 +23,24 @@ process.env.DEPOT_TOOLS_WIN_TOOLCHAIN = 0
 process.env.SCCACHE_BUCKET = 'electronjs-sccache'
 process.env.SCCACHE_TWO_TIER = 'true'
 
-// Paths to toolchains.
+// Help gn.py find the exe.
 process.env.CHROMIUM_BUILDTOOLS_PATH = path.resolve('src', 'buildtools')
+
+// Cleanup the cygwin paths in PATH, otherwise vpython will not work.
+if (process.platform === 'win32') {
+  let newPaths = []
+  const paths = process.env.PATH.split(path.delimiter)
+  for (const p of paths) {
+    if (p.startsWith('/'))
+      continue
+    if (p.includes('cygwin'))
+      continue
+    newPaths.push(p)
+  }
+  process.env.PATH = newPaths.join(path.delimiter)
+}
+
+// Add depot_tools to PATH.
 process.env.PATH = `${path.resolve('vendor', 'depot_tools')}${path.delimiter}${process.env.PATH}`
 
 if (process.platform === 'win32') {