fix tar unzip flag

Author: mks-m

Makefile

@@ -46,7 +46,7 @@ fetch_externals: $(EXTERNALS)/pypy externals.fetched
 externals.fetched:
 	echo https://github.com/pixie-lang/external-deps/releases/download/1.0/`uname -s`-`uname -m`.tar.bz2
 	curl -L https://github.com/pixie-lang/external-deps/releases/download/1.0/`uname -s`-`uname -m`.tar.bz2 > /tmp/externals.tar.bz2
-	tar -jxf /tmp/externals.tar.bz2 --strip-components=2
+	tar -zxf /tmp/externals.tar.bz2 --strip-components=2
 	touch externals.fetched
 
 $(EXTERNALS):
@@ -57,7 +57,7 @@ $(EXTERNALS)/pypy: $(EXTERNALS)
 	curl https://bitbucket.org/pypy/pypy/get/81254.tar.bz2 >  pypy.tar.bz2; \
 	mkdir pypy; \
 	cd pypy; \
-	tar -jxf ../pypy.tar.bz2 --strip-components=1
+	tar -zxf ../pypy.tar.bz2 --strip-components=1
 
 $(EXTERNALS)/re2: $(EXTERNALS)
 	cd $(EXTERNALS) && \