gyp: muffle xcode-select warnings

Muffle gyp from creating xcode-select related warnings, essentially
flooding the console.

Co-authored-by: Gibson Fahnestock <gibfahn@gmail.com>
Refs: nodejs/node-gyp#1370
Refs: #21520

Author: ryzokuken

tools/gyp/pylib/gyp/xcode_emulation.py

@@ -495,7 +495,7 @@ def _GetSdkVersionInfoItem(self, sdk, infoitem):
     # Since the CLT has no SDK paths anyway, returning None is the
     # most sensible route and should still do the right thing.
     try:
-      return GetStdout(['xcrun', '--sdk', sdk, infoitem])
+      return GetStdoutQuiet(['xcrun', '--sdk', sdk, infoitem])
     except:
       pass
 
@@ -1392,7 +1392,7 @@ def XcodeVersion():
   if XCODE_VERSION_CACHE:
     return XCODE_VERSION_CACHE
   try:
-    version_list = GetStdout(['xcodebuild', '-version']).splitlines()
+    version_list = GetStdoutQuiet(['xcodebuild', '-version']).splitlines()
     # In some circumstances xcodebuild exits 0 but doesn't return
     # the right results; for example, a user on 10.7 or 10.8 with
     # a bogus path set via xcode-select
@@ -1442,6 +1442,17 @@ def CLTVersion():
       continue
 
 
+def GetStdoutQuiet(cmdlist):
+  """Returns the content of standard output returned by invoking |cmdlist|.
+  Ignores the stderr.
+  Raises |GypError| if the command return with a non-zero return code."""
+  job = subprocess.Popen(cmdlist, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+  out = job.communicate()[0]
+  if job.returncode != 0:
+    raise GypError('Error %d running %s' % (job.returncode, cmdlist[0]))
+  return out.rstrip('\n')
+
+
 def GetStdout(cmdlist):
   """Returns the content of standard output returned by invoking |cmdlist|.
   Raises |GypError| if the command return with a non-zero return code."""