Fix matchcompiler failure in case of parallel build

During parallel build, multiple processes will try to create build_dir
in parallel, so the build will fail. Fix that by calling makedirs
unconditionally and ignoring errors from it. If there's actual
problem with directory creation, it'll be caught later by isdir()
check.

tools/matchcompiler.py

@@ -22,6 +22,7 @@ import sys
 import re
 import glob
 import argparse
+import errno
 
 
 class MatchCompiler:
@@ -667,8 +668,16 @@ def main():
         sys.exit(-1)
 
     # Create build directory if needed
-    if not os.path.exists(build_dir):
+    try:
         os.makedirs(build_dir)
+    except OSError as e:
+        # due to race condition in case of parallel build,
+        # makedirs may fail. Ignore that; if there's actual
+        # problem with directory creation, it'll be caught
+        # by the following isdir check
+        if e.errno != errno.EEXIST:
+            raise
+
     if not os.path.isdir(build_dir):
         raise Exception(build_dir + ' is not a directory')