Recursively delete conftest files

On OS X, one of the conftest files might be a directory named `conftest.dSYM`.

Makefile

@@ -278,7 +278,8 @@ clean:
 	rm -f $(SRC2:%.c=%.gcda) $(SRC2:%.c=%.gcno) *.dyn pgopti.dpi pgopti.dpi.lock *.pgd *.pgc
 
 distclean: clean
-	rm -f config.mak x264_config.h config.h config.log x264.pc x264.def conftest*
+	rm -f config.mak x264_config.h config.h config.log x264.pc x264.def
+	rm -rf conftest*
 
 install-cli: cli
 	$(INSTALL) -d $(DESTDIR)$(bindir)

configure

@@ -305,7 +305,8 @@ configure_system_override() {
     return $res
 }
 
-rm -f x264_config.h config.h config.mak config.log x264.pc x264.def conftest*
+rm -f x264_config.h config.h config.mak config.log x264.pc x264.def
+rm -rf conftest*
 
 # Construct a path to the specified directory relative to the working directory
 relative_path() {
@@ -540,7 +541,7 @@ host="${host#*-}"
 host_vendor="${host%%-*}"
 host_os="${host#*-}"
 
-trap 'rm -f conftest*' EXIT
+trap 'rm -rf conftest*' EXIT
 
 # test for use of compilers that require specific handling
 cc_base=`basename "$CC"`