Makefile.defs: use sed instead of awk for detecting glibc version

(cherry picked from commit 225a59475c91e154ce0a7f0ec252be841a5a8ce5)
(cherry picked from commit 17bbfe97179a2965b145b946b76ba458c2af8bd5)

src/Makefile.defs

@@ -1888,7 +1888,7 @@ ifeq ($(OS), linux)
 	endif
 	ifeq ($(CC_NAME), gcc)
 		# link librt for glibc <= 2.17
-		GLIBCVER:=$(shell ldd --version | head -1 | awk '{ sub(/\./, "", $NF); print $NF }' )
+		GLIBCVER=$(shell ldd --version | head -1 | sed -e 's/^.* //' -e 's/\.//' )
 		ifeq ($(shell [ $(GLIBCVER) -le 217 ] && echo librt), librt)
 			LIBS+=-lrt
 		endif