Avoid race between cmake and utf8_in_pwd tests

Summary:
The cmake test removes the _build dirs, and the utf8_in_pwd test
rsyncs them.

Reviewed By: akotulski

Differential Revision: D4375554

fbshipit-source-id: 3fa088c

infer/tests/build_systems/utf8_in_pwd/Makefile

@@ -47,7 +47,7 @@ $(UTF8_DIR):
 	$(MKDIR_P) $@
 
 $(CMAKE_DIR): $(CMAKE_SOURCES) $(UTF8_DIR)
-	rsync -aL $(CMAKE_SOURCES_DIR)/ $@/
+	rsync -aL --exclude='_build*' $(CMAKE_SOURCES_DIR)/ $@/
 	touch $@
 
 $(GRADLE_DIR): $(GRADLE_SOURCES) $(UTF8_DIR)