pkg/jerryscript: update rules

Remove unknown rules from .PHONY.
Make 'all' be the default target for jerryscript and execute `all` target.
This way no definition order issue could happen in the future.

pkg/jerryscript/Makefile

@@ -14,6 +14,6 @@ endif
 
 all: git-download
 	@cp Makefile.jerryscript $(PKG_BUILDDIR)/Makefile
-	"$(MAKE)" -C $(PKG_BUILDDIR)
+	"$(MAKE)" -C $(PKG_BUILDDIR) all
 
 include $(RIOTBASE)/pkg/pkg.mk

pkg/jerryscript/Makefile.jerryscript

@@ -8,9 +8,9 @@ ifeq ($(TOOLCHAIN)_$(BOARD),llvm_native)
   EXT_CFLAGS :=-D__TARGET_RIOT -Wno-conversion
 endif
 
-.PHONY: libjerry riot-jerry flash clean
+.PHONY: all libjerry
 
-# all: libjerry riot-jerry
+all: libjerry
 
 libjerry:
 	mkdir -p $(BUILD_DIR)