autotools: Use make clean for builds not supporting B != S

If the build doesn't support B != S, we can try running "make clean" instead
to try and clean up previous objects if the hash for the task has changed.

This tries to ensure that when variables like ${baselib} change, the changes are
correctly accounted for.

(From OE-Core rev: c2f761e2010857e2a2aad1dccf06ec39d15c1c86)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/autotools.bbclass

@@ -109,7 +109,11 @@ autotools_preconfigure() {
 			else
 				# At least remove the .la files since automake won't automatically
 				# regenerate them even if CFLAGS/LDFLAGS are different
-				cd ${S}; find ${S} -name \*.la -delete
+				cd ${S}
+				if [ -e Makefile -o -e makefile -o -e GNUmakefile ]; then
+					${MAKE} clean
+				fi
+				find ${S} -name \*.la -delete
 			fi
 		fi
 	fi