[get_clang_version] Make the version regex permissive

For instance, this will match `clang-dev` when using a local build of
llvm-toolchain.

Test: run script
Change-Id: I3f2a0a6adc360f0a299def79535ce139353aece2
diff --git a/scripts/get_clang_version.py b/scripts/get_clang_version.py
index 64d922a..691c45d 100755
--- a/scripts/get_clang_version.py
+++ b/scripts/get_clang_version.py
@@ -34,7 +34,7 @@
   with open(global_go) as infile:
     contents = infile.read()
 
-  regex_rev = r'\tClangDefaultVersion\s+= "(?P<rev>clang-r\d+[a-z]?\d?)"'
+  regex_rev = r'\tClangDefaultVersion\s+= "(?P<rev>clang-.*)"'
   match_rev = re.search(regex_rev, contents)
   if match_rev is None:
     raise RuntimeError('Parsing clang info failed')