slang: build system breaks with parallel builds

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/slang/slang.mk

@@ -9,7 +9,7 @@ SLANG_SITE = http://www.uclibc.org/
 SLANG_INSTALL_STAGING = YES
 
 define SLANG_BUILD_CMDS
-	$(MAKE) CC="$(TARGET_CC)" CFLAGS="$(TARGET_CFLAGS)" \
+	$(MAKE1) CC="$(TARGET_CC)" CFLAGS="$(TARGET_CFLAGS)" \
 	LDFLAGS="$(TARGET_LDFLAGS)" -C $(@D)
 endef