diff --git a/Makefile b/Makefile
index c8b16a3..dcab2d6 100644
--- a/Makefile
+++ b/Makefile
@@ -56,6 +56,13 @@ clean:
 distclean: clean
 	rm -rf sources
 
+check:
+	@echo "check bzip2"
+	@which bzip2
+	@echo "check gcc"
+	@which gcc
+	@echo "check libtool"
+	@which libtool
 
 # Rules for downloading and verifying sources. Treat an external SOURCES path as
 # immutable and do not try to download anything into it.
@@ -112,7 +119,7 @@ musl-git-%:
 	case "$@" in */*) exit 1 ;; esac
 	rm -rf $@.tmp
 	mkdir $@.tmp
-	( cd $@.tmp && tar zxvf - ) < $<
+	( cd $@.tmp && tar -zxvf - ) < $<
 	rm -rf $@
 	touch $@.tmp/$(patsubst %.orig,%,$@)
 	mv $@.tmp/$(patsubst %.orig,%,$@) $@
@@ -122,7 +129,7 @@ musl-git-%:
 	case "$@" in */*) exit 1 ;; esac
 	rm -rf $@.tmp
 	mkdir $@.tmp
-	( cd $@.tmp && tar jxvf - ) < $<
+	( cd $@.tmp && tar -jxvf - ) < $<
 	rm -rf $@
 	touch $@.tmp/$(patsubst %.orig,%,$@)
 	mv $@.tmp/$(patsubst %.orig,%,$@) $@
@@ -132,7 +139,7 @@ musl-git-%:
 	case "$@" in */*) exit 1 ;; esac
 	rm -rf $@.tmp
 	mkdir $@.tmp
-	( cd $@.tmp && tar Jxvf - ) < $<
+	( cd $@.tmp && tar -Jxvf - ) < $<
 	rm -rf $@
 	touch $@.tmp/$(patsubst %.orig,%,$@)
 	mv $@.tmp/$(patsubst %.orig,%,$@) $@
diff --git a/scripts/build.sh b/scripts/build.sh
index e78ebf3..8c4d6d3 100644
--- a/scripts/build.sh
+++ b/scripts/build.sh
@@ -59,7 +59,6 @@ function Build() {
         exit 1
     fi
     if [ ! "$TEST_BUILD_ONLY" ]; then
-        rm -rf output/${TARGET}
         tar -zcvf ${DIST}/${TARGET}.tgz output/*
         if [ $? -ne 0 ]; then
             echo "package ${TARGET} error"