cplc: Makefile - use pkg-config if xml2-config is not found

- GH #2199

(cherry picked from commit f05a46dc79de45c6cb958b845b9f2d85452c4f37)

src/modules/cplc/Makefile

@@ -7,6 +7,12 @@ NAME=cplc.so
 
 ifeq ($(CROSS_COMPILE),)
 XML2CFG=$(shell which xml2-config)
+ifeq ($(XML2CFG),)
+XML2CFG=$(shell \
+	if pkg-config --exists libxml-2.0; then \
+		echo 'pkg-config libxml-2.0'; \
+	fi)
+endif
 endif
 
 ifneq ($(XML2CFG),)