gyp: fix XCode CLT version detection on Catalina (nodejs#44)

* gyp: fix XCode CLT version detection on Catalina

Copies @szekelyisz nodejs#2141 to this repo.

* Regex loves raw strings

* Update pylib/gyp/xcode_emulation.py

Co-authored-by: Michaël Zasso <targos@protonmail.com>

Co-authored-by: Michaël Zasso <targos@protonmail.com>

pylib/gyp/xcode_emulation.py

@@ -1541,6 +1541,13 @@ def CLTVersion():
         except GypError:
             continue
 
+    regex = re.compile(r'Command Line Tools for Xcode\s+(?P<version>\S+)')
+    try:
+        output = GetStdout(["/usr/sbin/softwareupdate", "--history"])
+        return re.search(regex, output).groupdict()["version"]
+    except GypError:
+        return None
+
 
 def GetStdoutQuiet(cmdlist):
     """Returns the content of standard output returned by invoking |cmdlist|.